Attribute 'cf_returns_autoreleased' doesn't really exist.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@170723 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/Attr.td

@@ -234,11 +234,6 @@ def CFUnknownTransfer : InheritableAttr {
   let Subjects = [Function];
 }
 
-def CFReturnsAutoreleased : Attr {
-  let Spellings = [GNU<"cf_returns_autoreleased">];
-  let ASTNode = 0;
-}
-
 def CFReturnsRetained : InheritableAttr {
   let Spellings = [GNU<"cf_returns_retained">];
   let Subjects = [ObjCMethod, Function];