Reinstate "Nuke the old JIT."

Approved by Jim Grosbach, Lang Hames, Rafael Espindola.

This reinstates commits r215111, 215115, 215116, 215117, 215136.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216982 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86TargetMachine.cpp

@@ -157,10 +157,3 @@ bool X86PassConfig::addPreEmitPass() {
 
   return ShouldPrint;
 }
-
-bool X86TargetMachine::addCodeEmitter(PassManagerBase &PM,
-                                      JITCodeEmitter &JCE) {
-  PM.add(createX86JITCodeEmitterPass(*this, JCE));
-
-  return false;
-}