Add (redundant) #include "Experimental.h" in all .cpp files using the symbols

src/prefs/EffectsPrefs.cpp

@@ -29,6 +29,8 @@
 
 #include "EffectsPrefs.h"
 
+#include "../Experimental.h"
+
 EffectsPrefs::EffectsPrefs(wxWindow * parent)
 :  PrefsPanel(parent, _("Effects"))
 {

src/prefs/GUIPrefs.cpp

@@ -29,6 +29,8 @@
 
 #include "GUISettings.h"
 
+#include "../Experimental.h"
+
 GUIPrefs::GUIPrefs(wxWindow * parent)
 :  PrefsPanel(parent, _("Interface"))
 {

src/prefs/LibraryPrefs.cpp

@@ -29,6 +29,8 @@ MP3 and FFmpeg encoding libraries.
 
 #include "LibraryPrefs.h"
 
+#include "../Experimental.h"
+
 ////////////////////////////////////////////////////////////////////////////////
 
 #define ID_MP3_FIND_BUTTON          7001

src/prefs/RecordingPrefs.cpp

@@ -30,6 +30,8 @@
 #include "../Prefs.h"
 #include "../ShuttleGui.h"
 
+#include "../Experimental.h"
+
 using std::min;
 
 RecordingPrefs::RecordingPrefs(wxWindow * parent)

src/prefs/SpectrogramSettings.cpp

@@ -27,6 +27,8 @@ Paul Licameli
 
 #include <cmath>
 
+#include "../Experimental.h"
+
 SpectrogramSettings::Globals::Globals()
 {
    LoadPrefs();

src/prefs/SpectrumPrefs.cpp

@@ -30,6 +30,8 @@
 
 #include <algorithm>
 
+#include "../Experimental.h"
+
 SpectrumPrefs::SpectrumPrefs(wxWindow * parent, WaveTrack *wt)
 :  PrefsPanel(parent, wt ? _("Spectrogram Settings") : _("Spectrograms"))
 , mWt(wt)

src/prefs/TracksPrefs.cpp

@@ -28,6 +28,8 @@
 #include "../ShuttleGui.h"
 #include "../WaveTrack.h"
 
+#include "../Experimental.h"
+
 ////////////////////////////////////////////////////////////////////////////////
 
 TracksPrefs::TracksPrefs(wxWindow * parent)