Revert "[X86] Adding new LLVM TableGen backend that generates the X86 backend...

Revert "[X86] Adding new LLVM TableGen backend that generates the X86 backend memory folding tables."

This reverts commit 28cb1003507f287726f43c771024a1dc102c45fe as well
as all subsequent followups.  llvm-tblgen currently segfaults with
this change, and it seems it has been broken on the bots all
day with no fixes in preparation.  See, for example:

http://lab.llvm.org:8011/builders/clang-x86-windows-msvc2015/

llvm-svn: 304121