Fix some 'declaration hides' warnings.

We were for example getting many of these:
\audacity\src\widgets\numerictextctrl.h(171): warning C4458: declaration of 'value' hides class member

MSVC2013 didn't warn about these, but MSVC2017 does.

src/commands/ScreenshotCommand.cpp

@@ -315,7 +315,7 @@ bool ScreenshotCommand::CaptureToolbar(
 
 bool ScreenshotCommand::CaptureDock(
    const CommandContext & context,
-   wxWindow *win, const wxString &mFileName)
+   wxWindow *win, const wxString &FileName)
 {
    int x = 0, y = 0;
    int width, height;
@@ -324,7 +324,7 @@ bool ScreenshotCommand::CaptureDock(
    win->GetParent()->ScreenToClient(&x, &y);
    win->GetClientSize(&width, &height);
 
-   return Capture(context, mFileName, win, wxRect(x, y, width, height));
+   return Capture(context, FileName, win, wxRect(x, y, width, height));
 }
 
 void ExploreMenu(
@@ -410,17 +410,17 @@ void ScreenshotCommand::CaptureWindowOnIdle(
 
 void ScreenshotCommand::CapturePreferences( 
    const CommandContext & context,
-   AudacityProject * pProject, const wxString &mFileName ){
-   (void)&mFileName;//compiler food.
+   AudacityProject * pProject, const wxString &FileName ){
+   (void)&FileName;//compiler food.
    (void)&context;
    CommandManager * pMan = pProject->GetCommandManager();
 
    // Yucky static variables.  Is there a better way?  The problem is that we need the
    // idle callback to know more about what to do.
 #ifdef __WXMSW__
-   mDirToWriteTo = mFileName.BeforeLast('\\') + "\\";
+   mDirToWriteTo = FileName.BeforeLast('\\') + "\\";
 #else
-   mDirToWriteTo = mFileName.BeforeLast('/') + "/";
+   mDirToWriteTo = FileName.BeforeLast('/') + "/";
 #endif
    mpShooter = this;
    const int nPrefsPages = 19;
@@ -431,8 +431,8 @@ void ScreenshotCommand::CapturePreferences(
       gPrefs->Write(wxT("/Prefs/PrefsCategory"), (long)i);
       gPrefs->Flush();
       wxString Command = "Preferences";
-      const CommandContext context( *pProject );
-      if( !pMan->HandleTextualCommand( Command, context, AlwaysEnabledFlag, AlwaysEnabledFlag ) )
+      const CommandContext projectContext( *pProject );
+      if( !pMan->HandleTextualCommand( Command, projectContext, AlwaysEnabledFlag, AlwaysEnabledFlag ) )
       {
          wxLogDebug("Command %s not found", Command );
       }
@@ -444,10 +444,10 @@ void ScreenshotCommand::CapturePreferences(
 
 void ScreenshotCommand::CaptureEffects(
    const CommandContext & context,
-   AudacityProject * pProject, const wxString &mFileName )
+   AudacityProject * pProject, const wxString &FileName )
 {
    (void)pProject;
-   (void)&mFileName;//compiler food.
+   (void)&FileName;//compiler food.
    (void)&context;
 #define TRICKY_CAPTURE
 #define CAPTURE_NYQUIST_TOO
@@ -537,10 +537,10 @@ void ScreenshotCommand::CaptureEffects(
 
 void ScreenshotCommand::CaptureScriptables( 
    const CommandContext & context,
-   AudacityProject * pProject, const wxString &mFileName )
+   AudacityProject * pProject, const wxString &FileName )
 {
    (void)pProject;
-   (void)&mFileName;//compiler food.
+   (void)&FileName;//compiler food.
    (void)&context;
 
    const wxString ScriptablesNames[] = {
@@ -595,8 +595,8 @@ void ScreenshotCommand::CaptureCommands(
       // The handler is cleared each time it is used.
       SetIdleHandler( IdleHandler );
       Str = Commands[i];
-      const CommandContext context( *pProject );
-      if( !pMan->HandleTextualCommand( Str, context, AlwaysEnabledFlag, AlwaysEnabledFlag ) )
+      const CommandContext projectContext( *pProject );
+      if( !pMan->HandleTextualCommand( Str, projectContext, AlwaysEnabledFlag, AlwaysEnabledFlag ) )
       {
          wxLogDebug("Command %s not found", Str);
       }

src/effects/Distortion.cpp

@@ -1190,7 +1190,7 @@ void EffectDistortion::Leveller()
    // Here we model that more efficiently by repeated passes over a linear table.
    for (int n = STEPS; n < TABLESIZE; n++) {
       mTable[n] = ((double) (n - STEPS) / (double) STEPS);
-      for (int i = 0; i < numPasses; i++) {
+      for (int j = 0; j < numPasses; j++) {
          // Find the highest index for gain adjustment
          int index = numPoints - 1;
          for (int i = index; i >= 0 && mTable[n] < gainLimits[i]; i--) {

src/effects/NoiseReduction.cpp

@@ -650,7 +650,7 @@ EffectNoiseReduction::Worker::~Worker()
 
 bool EffectNoiseReduction::Worker::Process
 (EffectNoiseReduction &effect, Statistics &statistics, TrackFactory &factory,
- SelectedTrackListOfKindIterator &iter, double mT0, double mT1)
+ SelectedTrackListOfKindIterator &iter, double inT0, double inT1)
 {
    int count = 0;
    WaveTrack *track = (WaveTrack *) iter.First();
@@ -665,8 +665,8 @@ bool EffectNoiseReduction::Worker::Process
 
       double trackStart = track->GetStartTime();
       double trackEnd = track->GetEndTime();
-      double t0 = std::max(trackStart, mT0);
-      double t1 = std::min(trackEnd, mT1);
+      double t0 = std::max(trackStart, inT0);
+      double t1 = std::min(trackEnd, inT1);
 
       if (t1 > t0) {
          auto start = track->TimeToLongSamples(t0);

src/ondemand/ODComputeSummaryTask.cpp

@@ -66,7 +66,7 @@ void ODComputeSummaryTask::DoSomeInternal()
    }
 
    mBlockFilesMutex.Lock();
-   for(size_t i=0; i < mWaveTracks.size() && mBlockFiles.size();i++)
+   for(size_t j=0; j < mWaveTracks.size() && mBlockFiles.size();j++)
    {
       bool success = false;
       const auto bf = mBlockFiles[0].lock();

src/ondemand/ODDecodeTask.cpp

@@ -43,7 +43,7 @@ void ODDecodeTask::DoSomeInternal()
 
    ODFileDecoder* decoder;
 
-   for(size_t i=0; i < mWaveTracks.size() && mBlockFiles.size();i++)
+   for(size_t j=0; j < mWaveTracks.size() && mBlockFiles.size();j++)
    {
       const auto bf = mBlockFiles[0].lock();
       sampleCount blockStartSample = 0;

src/prefs/MidiIOPrefs.cpp

@@ -207,8 +207,6 @@ void MidiIOPrefs::OnHost(wxCommandEvent & WXUNUSED(e))
          wxString device = wxString::Format(wxT("%s: %s"),
                                             interf,
                                             name);
-         int index;
-
          if (info->output) {
             playnames.Add(name);
             index = mPlay->Append(name, (void *) info);

src/widgets/Meter.cpp

@@ -1649,7 +1649,7 @@ void MeterPanel::DrawMeterBar(wxDC &dc, MeterBar *bar)
          // Draw the "recent" peak hold line
          // (h - 1) corresponds to the mRuler.SetBounds() in HandleLayout()
          dc.SetPen(mPen);
-         int ht = (int)(bar->peakHold * (h - 1) + 0.5);
+         ht = (int)(bar->peakHold * (h - 1) + 0.5);
          if (ht > 0)
          {
             AColor::Line(dc, x, y + h - ht - 1, x + w - 1, y + h - ht - 1);

src/widgets/NumericTextCtrl.h

@@ -168,14 +168,14 @@ class NumericTextCtrl final : public wxControl, public NumericConverter
 
       Options() {}
 
-      Options &AutoPos (bool value) { autoPos = value; return *this; }
-      Options &ReadOnly (bool value) { readOnly = value; return *this; }
-      Options &MenuEnabled (bool value) { menuEnabled = value; return *this; }
-      Options &InvalidValue (bool has, double value = -1.0)
-         { hasInvalidValue = has, invalidValue = value; return *this; }
+      Options &AutoPos (bool enable) { autoPos = enable; return *this; }
+      Options &ReadOnly (bool enable) { readOnly = enable; return *this; }
+      Options &MenuEnabled (bool enable) { menuEnabled = enable; return *this; }
+      Options &InvalidValue (bool has, double v = -1.0)
+         { hasInvalidValue = has, invalidValue = v; return *this; }
       // use a custom format not in the tables:
-      Options &Format (const wxString &value)
-         { format = value; return *this; }
+      Options &Format (const wxString &f)
+         { format = f; return *this; }
       Options &Value (bool has, double v)
          { hasValue = has, value = v; return *this; }
    };