Merge function-return.c into function.c

Fix PR2790 by making a warning an EXTWARN instead of EXTENSION.
Add a new EXTENSION warning for "return (some void expression);"


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@61187 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Parser/objc-try-catch-1.m b/test/Parser/objc-try-catch-1.m
index d8264fa..2e3c5b1 100644
--- a/test/Parser/objc-try-catch-1.m
+++ b/test/Parser/objc-try-catch-1.m
@@ -60,6 +60,6 @@
     @try {
         // Do something
     } @catch (...) {}
-    return 0;
+    return;
 }