The returns_nonnull attribute does not require a function prototype because it...

The returns_nonnull attribute does not require a function prototype because it affects only the return value, not any arguments. In turn, asking for a function or method result type should not require a function prototype either, so getFunctionOrMethodResultType has been relaxed.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@212827 91177308-0d34-0410-b5e6-96231b3b80d8