moc: remove _MSC_EXTENSIONS #define

Because we obviously don't support Microsoft's extensions in C++. This
is required because some MS headers have code that isn't proper C++,
like iso646.h:

 #if !defined(__cplusplus) || defined(_MSC_EXTENSIONS)
  #define and   &&

Change-Id: Ib57b52598e2f452985e9fffd145a3d4ec28e773d
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

src/tools/moc/main.cpp

@@ -422,6 +422,9 @@ int runMoc(int argc, char **argv)
     // 1. preprocess
     moc.symbols = pp.preprocessed(moc.filename, &in);
 
+    // We obviously do not support MS extensions
+    pp.macros.remove("_MSC_EXTENSIONS");
+
     if (!pp.preprocessOnly) {
         // 2. parse
         moc.parse();