This will make it easier to find the LICENSE and some
software also looks in the root to automatically find it.

Reviewed By: kristof.beyls, lattner

Differential Revision: https://reviews.llvm.org/D132018

Summary:
This commit is the first step in rebasing all of BOLT
history in the LLVM monorepo. It also solves trivial build issues
by updating BOLT codebase to use current LLVM. There is still work
left in rebasing some BOLT features and in making sure everything
is working as intended.

History has been rewritten to put BOLT in the /bolt folder, as
opposed to /tools/llvm-bolt.

(cherry picked from FBD33289252)

Summary:
BOLT sources are being moved under tools/llvm-bolt/src
and tools/llvm-bolt will contain more files such as LICENSE.txt,
README.txt, etc.

Remove trailing white spaces from our sources.

Create llvm.patch by running

  > git diff f137ed238db11440f03083b1c88b7ffc0f4af65e include lib > \
    tools/llvm-bolt/llvm.patch

README.txt has instructions on checking out sources and applying the
patch.

(cherry picked from FBD7878380)