[clang] trivial error msg fix

[Nathan Sidwell]

In developing a different warning patch, I came across this English grammar 
malfunction in the error messages.  This use of 'which' requires a preceding comma.

testing showed no regression, so I presume this diagnostic does not have a test 
case.

ok?

nathan
-------------- next part --------------
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td	(revision 222776)
+++ include/clang/Basic/DiagnosticSemaKinds.td	(working copy)
@@ -5269,7 +5273,7 @@ def err_bad_cxx_cast_member_pointer_size
   "cannot %select{||reinterpret_cast||C-style cast|}0 from member pointer "
   "type %1 to member pointer type %2 of different size">;
 def err_bad_reinterpret_cast_reference : Error<
-  "reinterpret_cast of a %0 to %1 needs its address which is not allowed">;
+  "reinterpret_cast of a %0 to %1 needs its address, which is not allowed">;
 def warn_undefined_reinterpret_cast : Warning<
   "reinterpret_cast from %0 to %1 has undefined behavior">,
   InGroup<UndefinedReinterpretCast>, DefaultIgnore;