Tweak wording and add diagnostic groups to misc diagnostics.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167274 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Sema/exprs.c b/test/Sema/exprs.c
index a93e12e..df3e258 100644
--- a/test/Sema/exprs.c
+++ b/test/Sema/exprs.c
@@ -40,7 +40,7 @@
 }
 
 _Complex double test2() {
-  return 1.0if;    // expected-warning {{imaginary constants are an extension}}
+  return 1.0if;    // expected-warning {{imaginary constants are a GNU extension}}
 }
 
 // rdar://6097308