Prep work to handle input chains of matched patterns and checking for

Prep work to handle input chains of matched patterns and checking for
'ischaincompatible' when a pattern has more than one input chain.  Need
to do some commenting and cleanup now that I understand how this works.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96443 91177308-0d34-0410-b5e6-96231b3b80d8