Revert "Exposing MCJIT through C API"

This reverts commit 8c31b298149ca3c3f2bbd9e8aa9a01c4d91f3d74.

It looks like this commit broke some bots:

http://lab.llvm.org:8011/builders/llvm-ppc64-linux2/builds/5209

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180248 91177308-0d34-0410-b5e6-96231b3b80d8