Using 'new-style' AssertMacros to support compilation for macOS 10.3 and iOS 11

To avoid collisions with boost and c++ standard library using the assert macros starting with two underscores is the default under these new SDKs. Since they already existed in our minimum deploment SDK we can switch them safely.

src/common/filefn.cpp

@@ -866,7 +866,7 @@ void wxMacFilename2FSSpec( const wxString& path , FSSpec *spec )
     FSRef fsRef;
     wxMacPathToFSRef( path , &fsRef );
     err = FSGetCatalogInfo(&fsRef, kFSCatInfoNone, NULL, NULL, spec, NULL);
-    verify_noerr( err );
+    __Verify_noErr(err);
 }
 #endif