Add wxGCC_WARNING_{SUPPRESS,RESTORE} macros and use them for -Wfloat-equal.

Suppress the warnings about comparing floating point values for equality in
wxWidgets headers when the user code is compiled with -Wfloat-equal (at least
when using g++ 4.6 or later).

Closes #14895.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73280 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/defs.h

@@ -583,6 +583,27 @@ typedef short int WXTYPE;
 #   define wxDEPRECATED_BUT_USED_INTERNALLY(x) wxDEPRECATED(x)
 #endif
 
+/*
+   Macros to suppress and restore gcc warnings, requires g++ >= 4.6 and don't
+   do anything otherwise.
+
+   Example of use:
+
+        wxGCC_WARNING_SUPPRESS(float-equal)
+        inline bool wxIsSameDouble(double x, double y) { return x == y; }
+        wxGCC_WARNING_RESTORE(float-equal)
+ */
+#if wxCHECK_GCC_VERSION(4, 6)
+#   define wxGCC_WARNING_SUPPRESS(x) \
+        _Pragma (wxSTRINGIZE(GCC diagnostic push)) \
+        _Pragma (wxSTRINGIZE(GCC diagnostic ignored wxSTRINGIZE(wxCONCAT(-W,x))))
+#   define wxGCC_WARNING_RESTORE(x) \
+       _Pragma (wxSTRINGIZE(GCC diagnostic pop))
+#else /* gcc < 4.6 or not gcc at all */
+#   define wxGCC_WARNING_SUPPRESS(x)
+#   define wxGCC_WARNING_RESTORE(x)
+#endif
+
 /*
     Combination of the two variants above: should be used for deprecated
     functions which are defined inline and are used by wxWidgets itself.