Have AttributeSet::getRetAttributes() return an AttributeSet instead of Attribute.

This further restricts the use of the Attribute class to the Attribute family of
classes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173098 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed