VS8/9: Add flag map entries for /Zc:wchar_t (#10397)

Source/cmGlobalVisualStudio8Generator.cxx

@@ -358,8 +358,14 @@ static cmVS7FlagTable cmVS8ExtraFlagTable[] =
   {"ExceptionHandling", "EHsc", "enable c++ exceptions", "1", 0},
   {"ExceptionHandling", "EHa", "enable SEH exceptions", "2", 0},
 
-  {"EnablePREfast", "analyze", "", "TRUE", 0},
-  {"EnablePREfast", "analyze-", "", "FALSE", 0},
+  {"EnablePREfast", "analyze", "", "true", 0},
+  {"EnablePREfast", "analyze-", "", "false", 0},
+
+  // Language options
+  {"TreatWChar_tAsBuiltInType", "Zc:wchar_t",
+   "wchar_t is a built-in type", "true", 0},
+  {"TreatWChar_tAsBuiltInType", "Zc:wchar_t-",
+   "wchar_t is not a built-in type", "false", 0},
 
   {0,0,0,0,0}
 };