Changed declarations from Attr to InheritableAttr as they are already being processed that way semantically.

Patch thanks to Dean Sutherland!  Reviewed by Eli Friedman.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186598 91177308-0d34-0410-b5e6-96231b3b80d8