Add target analysis passes to the codegen pipeline for MCJIT.

This patch adds the target analysis passes (usually TargetTransformInfo) to the
codgen pipeline. We also expose now the AddAnalysisPasses method through the C
API, because the optimizer passes would also benefit from better target-specific
cost models.

Reviewed by Andrew Kaylor

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199926 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ExecutionEngine/ExecutionEngine.h

@@ -462,6 +462,9 @@ public:
     llvm_unreachable("No support for an object cache");
   }
 
+  /// Return the target machine (if available).
+  virtual TargetMachine *getTargetMachine() { return NULL; }
+
   /// DisableLazyCompilation - When lazy compilation is off (the default), the
   /// JIT will eagerly compile every function reachable from the argument to
   /// getPointerToFunction.  If lazy compilation is turned on, the JIT will only