Replace '#include ValueTypes.h' with forward declarations.

In some cases the include is pushed "downstream" (or removed if
unused).

llvm-svn: 203644
diff --git a/llvm/lib/Target/X86/InstPrinter/X86InstComments.cpp b/llvm/lib/Target/X86/InstPrinter/X86InstComments.cpp
index 50ee968..f81624e 100644
--- a/llvm/lib/Target/X86/InstPrinter/X86InstComments.cpp
+++ b/llvm/lib/Target/X86/InstPrinter/X86InstComments.cpp
@@ -16,7 +16,9 @@
 #include "MCTargetDesc/X86MCTargetDesc.h"
 #include "Utils/X86ShuffleDecode.h"
 #include "llvm/MC/MCInst.h"
+#include "llvm/CodeGen/ValueTypes.h"
 #include "llvm/Support/raw_ostream.h"
+
 using namespace llvm;
 
 //===----------------------------------------------------------------------===//