Don't test for old compilers in C++11 mode in configure

This makes configure faster when C++11 is enabled by avoiding spending time on
compiling unnecessary checks in this case.

include/wx/wxcrtbase.h

@@ -183,6 +183,16 @@ extern unsigned long android_wcstoul(const wchar_t *nptr, wchar_t **endptr, int
     #define wxCRT_StrtollW   _wcstoi64
     #define wxCRT_StrtoullW  _wcstoui64
 #else
+    /* Both of these functions are implemented in C++11 compilers */
+    #if defined(__cplusplus) && __cplusplus >= 201103L
+        #ifndef HAVE_STRTOULL
+            #define HAVE_STRTOULL
+        #endif
+        #ifndef HAVE_WCSTOULL
+            #define HAVE_WCSTOULL
+        #endif
+    #endif
+
     #ifdef HAVE_STRTOULL
         #define wxCRT_StrtollA   strtoll
         #define wxCRT_StrtoullA  strtoull