Add a warning to ctype<char>::classic_table() if not implemented.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@151728 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/locale.cpp b/src/locale.cpp
index 089fae6..109629d 100644
--- a/src/locale.cpp
+++ b/src/locale.cpp
@@ -940,6 +940,7 @@
 #else
     // Platform not supported: abort so the person doing the port knows what to
     // fix
+# warning  ctype<char>::classic_table() is not implemented
     abort();
     return NULL;
 #endif