Prune some includes and forward declarations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153415 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/TargetMachine.cpp b/lib/Target/TargetMachine.cpp
index b4969ca..493a8f1 100644
--- a/lib/Target/TargetMachine.cpp
+++ b/lib/Target/TargetMachine.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCCodeGenInfo.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Support/CommandLine.h"