Add windows definitions to make the code model happy.

__stdcall for all compilers (MSVC and MinGW, possibly others may use it)
__w64 is MSVC only, deprecated there, but still used in some places

Reviewed-By: Roberto Raggi
(cherry picked from commit 5832c6b584)

src/plugins/cpptools/cppmodelmanager.cpp

@@ -152,6 +152,7 @@ static const char pp_configuration[] =
 
     // ### add macros for win32
     "#define __cdecl\n"
+    "#define __stdcall\n"
     "#define QT_WA(x) x\n"
     "#define API\n"
     "#define WINAPI\n"