Fix a conflict between the backported number validator and formatter

When building for wx3 on Linux, the backported number validators
and formatter conflicts with the wx3 version because I never
renamed them.  Crashes during termination would occur because
the wx3 version and our version had different vtables.

I was thinking that we would just be able to delete the
backported version when upgrading to wx3, but since
we've made Audacity specific changes to them we can't
simply start using the real wx3 versions anymore.

Therefore, I needed to rename then to prevent the crashes.

src/effects/VST/VSTEffect.cpp

@@ -786,7 +786,7 @@ void VSTEffectOptionsDialog::PopulateOrExchange(ShuttleGui & S)
       {
          S.StartStatic(_("Buffer Size"));
          {
-            wxIntegerValidator<int> vld(&mBufferSize);
+            IntegerValidator<int> vld(&mBufferSize);
             vld.SetRange(8, 1048576 * 1);
 
             S.AddVariableText(wxString() +