Switching the common attribute over to using the generic diagnostic, and removing the now-unused diagnostic. Updates a test case.

llvm-svn: 195581
diff --git a/clang/test/SemaCXX/attr-common.cpp b/clang/test/SemaCXX/attr-common.cpp
index 58b3013..fb98639 100644
--- a/clang/test/SemaCXX/attr-common.cpp
+++ b/clang/test/SemaCXX/attr-common.cpp
@@ -1,3 +1,3 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 
-__attribute__((common)) int x; // expected-error {{common attribute is not supported in C++}}
+__attribute__((common)) int x; // expected-error {{'common' attribute is not supported in C++}}