Remove the Forward Control Flow Integrity pass and its dependencies.

Remove the Forward Control Flow Integrity pass and its dependencies.

This work is currently being rethought along different lines and
if this work is needed it can be resurrected out of svn. Remove it
for now as no current work in ongoing on it and it's unused. Verified
with the authors before removal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230780 91177308-0d34-0410-b5e6-96231b3b80d8