Use the AttributeSet as the 'key' to the map instead of the 'raw' pointer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174950 91177308-0d34-0410-b5e6-96231b3b80d8
Have the bitcode writer and reader handle the new attribute references.

The bitcode writer emits a reference to the attribute group that the object at
the given index refers to. The bitcode reader is modified to read this in and
map it back to the attribute group.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174952 91177308-0d34-0410-b5e6-96231b3b80d8