VS 14: Add flag map for -std= to CppLanguageStandard tag in project files

This is used by the Clang/C2 toolset.

Source/cmVS14CLFlagTable.h

@@ -174,6 +174,24 @@ static cmVS7FlagTable cmVS14CLFlagTable[] =
   {"CompileAsManaged", "clr:oldSyntax",
    "Common Language RunTime Support, Old Syntax", "OldSyntax", 0},
 
+  {"CppLanguageStandard", "",
+   "Default", "Default", 0},
+  {"CppLanguageStandard", "std=c++98",
+   "C++03", "c++98", 0},
+  {"CppLanguageStandard", "std=c++11",
+   "C++11", "c++11", 0},
+  {"CppLanguageStandard", "std=c++1y",
+   "C++14", "c++1y", 0 },
+  {"CppLanguageStandard", "std=c++14",
+   "C++14", "c++1y", 0 },
+  {"CppLanguageStandard", "std=gnu++98",
+   "C++03 (GNU Dialect)", "gnu++98", 0},
+  {"CppLanguageStandard", "std=gnu++11",
+   "C++11 (GNU Dialect)", "gnu++11", 0},
+  {"CppLanguageStandard", "std=gnu++1y",
+   "C++14 (GNU Dialect)", "gnu++1y", 0},
+  {"CppLanguageStandard", "std=gnu++14",
+   "C++14 (GNU Dialect)", "gnu++1y", 0},
 
   //Bool Properties
   {"CompileAsWinRT", "ZW", "", "true", 0},