Remove a few unnecessary includes
Move InstMapping and PrintReplacement to Inst library
Add Parser library

This is for parsing instructions in souper inst format. The intention is
that the output of the souper command can be piped directly into this.
Add souperweb tool

This is a web based tool that can be used to harvest simplifications from
LLVM IR, or to check user-supplied simplifications in inst format.
Merge remote-tracking branch 'upstream/master' into undefined_behavior