Revert "[FastISel][X86] Remove no longer needed functions."
Revert "[FastISel][X86] Implement the FastLowerIntrinsicCall hook."
Revert "[FastISel][X86] Implement the FastLowerCall hook."

This reverts commit r213035, r213036, and r213037 to make the
buildbots happy again.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213048 91177308-0d34-0410-b5e6-96231b3b80d8