Push some more methods down to hide the use of the Attribute class.

Because the Attribute class is going to stop representing a collection of
attributes, limit the use of it as an aggregate in favor of using AttributeSet.
This replaces some of the uses for querying the function attributes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172844 91177308-0d34-0410-b5e6-96231b3b80d8