Don't define _CRTBLD when using MSVC 12 or later.

This results in fatal #errors from the standard <assert.h> which doesn't want
to be included with _CRTBLD defined. Generally speaking, defining _CRTBLD
looks like a very wrong thing to do and it's probably not necessary any more
(considering that it was done in r25683 almost 10 years ago) but only avoid
doing this with VC 12 for now to avoid breaking anything else before 3.0.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@75093 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/msvcrt.h

@@ -37,7 +37,12 @@
     #endif
 
     #include <stdlib.h>
-    #ifndef _CRTBLD
+
+    // Defining _CRTBLD should never be necessary at all, but keep it for now
+    // as there is no time to retest all the compilers before 3.0 release.
+    // Definitely do not use it with MSVS 2013 as defining it results in errors
+    // if the standard <assert.h> is included afterwards.
+    #if !defined(_CRTBLD) && !wxCHECK_VISUALC_VERSION(12)
         // Needed when building with pure MS SDK
         #define _CRTBLD
     #endif