Remove harmless unused variables warnings in non-debug build

Suppress a few -Wunused-variable and -Wunused-parameter warnings when
using --disable-debug.

src/common/webrequest.cpp

@@ -46,8 +46,10 @@ extern WXDLLIMPEXP_DATA_NET(const char) wxWebSessionBackendCURL[] = "CURL";
 wxDEFINE_EVENT(wxEVT_WEBREQUEST_STATE, wxWebRequestEvent);
 wxDEFINE_EVENT(wxEVT_WEBREQUEST_DATA, wxWebRequestEvent);
 
+#ifdef __WXDEBUG__
 static const wxStringCharType* wxNO_IMPL_MSG
     = wxS("can't be used with an invalid/uninitialized object");
+#endif
 
 #define wxCHECK_IMPL(rc) wxCHECK_MSG( m_impl, (rc), wxNO_IMPL_MSG )
 #define wxCHECK_IMPL_VOID() wxCHECK_RET( m_impl, wxNO_IMPL_MSG )

src/osx/core/bitmap.cpp

@@ -1411,19 +1411,19 @@ bool wxBitmap::HasAlpha() const
 }
 
 #if WXWIN_COMPATIBILITY_3_0
-void wxBitmap::SetWidth(int w)
+void wxBitmap::SetWidth(int WXUNUSED_UNLESS_DEBUG(w))
 {
     AllocExclusive();
     wxASSERT_MSG( GetWidth() == w, "Changing the bitmap width is not supported");
 }
 
-void wxBitmap::SetHeight(int h)
+void wxBitmap::SetHeight(int WXUNUSED_UNLESS_DEBUG(h))
 {
     AllocExclusive();
     wxASSERT_MSG( GetHeight() == h, "Changing the bitmap height is not supported");
 }
 
-void wxBitmap::SetDepth(int d)
+void wxBitmap::SetDepth(int WXUNUSED_UNLESS_DEBUG(d))
 {
     AllocExclusive();
     wxASSERT_MSG( d == -1 || GetDepth() == d, "Changing the bitmap depth is not supported");

src/osx/core/display.cpp

@@ -226,6 +226,7 @@ int wxDisplayFactoryMacOSX::GetFromPoint(const wxPoint& p)
     CGDisplayCount theCount;
     CGDisplayErr err = CGGetDisplaysWithPoint(thePoint, 1, &theID, &theCount);
     wxASSERT(err == CGDisplayNoErr);
+    wxUnusedVar(err); // suppress "unused" warning in non-debug builds
 
     if (theCount)
         return wxOSXGetDisplayFromID(theID);