Disable warnings in the standard shlobj.h header with MSVC14

There is nothing we can do about these (harmless) warnings, so just
disable them. Also make sure that the header is included via
wx/msw/wrapshl.h  everywhere.

(backported from commit e37f1a84ce)

include/wx/msw/wrapshl.h

@@ -20,8 +20,21 @@
     #include <shellapi.h>
 #endif
 
+#ifdef __VISUALC__
+    // Disable a warning that we can do nothing about: we get it for
+    // shlobj.h at least from 7.1a Windows kit when using VC14.
+    #pragma warning(push)
+
+    // 'typedef ': ignored on left of '' when no variable is declared
+    #pragma warning(disable:4091)
+#endif
+
 #include <shlobj.h>
 
+#ifdef __VISUALC__
+    #pragma warning(pop)
+#endif
+
 #include "wx/msw/winundef.h"
 
 #include "wx/log.h"