Add a DenseMapInfo class for the AttributeSet.

We are going to place the AttributeSet into a DenseMap during assembly writing.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174812 91177308-0d34-0410-b5e6-96231b3b80d8
TEMPORARY SYNTAX CHANGE!

The original syntax for the attribute groups was ambiguous. For example:

    declare void @foo() #1
    #0 = attributes { noinline }

The '#0' would be parsed as an attribute reference for '@foo' and not as a
top-level entity. In order to continue forward while waiting for a decision on
what the correct syntax is, I'm changing it to this instead:

     declare void @foo() #1
     attributes #0 = { noinline }

Repeat: This is TEMPORARY until we decide what the correct syntax should be.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174813 91177308-0d34-0410-b5e6-96231b3b80d8