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

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