[Loop Peeling] Enable peeling for loops with multiple exits

This CL enables peeling of the loop with multiple exits where
one exit should be from latch and others are basic blocks with
call to deopt.

The peeling is enabled under the flag which is false by default.

Reviewers: reames, mkuper, iajbar, fhahn
Reviewed By: reames
Subscribers: xbolva00, hiraditya, zzheng, llvm-commits
Differential Revision: https://reviews.llvm.org/D63923

llvm-svn: 366048