Add wxOSX_10_6_AND_LATER macro and use it.

Replace all occurrences of

	@interface wxFoo : NSFoo
	#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_6
	    <NSProtocol>
	#endif

which we used for protocols new in 10.6 with just

	@interface wxFoo : NSFoo wxOSX_10_6_AND_LATER(<NSProtocol>)

which looks better and simpler.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62755 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/core/private.h

@@ -21,6 +21,17 @@
 #include "wx/osx/core/cfstring.h"
 #include "wx/osx/core/cfdataref.h"
 
+// Define helper macros allowing to insert small snippets of code to be
+// compiled for high enough OS X version only: this shouldn't be abused for
+// anything big but it's handy for e.g. specifying OS X 10.6-only protocols in
+// the Objective C classes declarations when they're not supported under the
+// previous versions
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_6
+    #define wxOSX_10_6_AND_LATER(x) x
+#else
+    #define wxOSX_10_6_AND_LATER(x)
+#endif
+
 #if wxOSX_USE_COCOA_OR_CARBON
 
 WXDLLIMPEXP_BASE long UMAGetSystemVersion() ;