Reorder includes in Target backends to following coding standards. Remove some superfluous forward declarations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152997 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86Subtarget.h b/lib/Target/X86/X86Subtarget.h
index a36d0d8..7fd832b 100644
--- a/lib/Target/X86/X86Subtarget.h
+++ b/lib/Target/X86/X86Subtarget.h
@@ -14,9 +14,9 @@
 #ifndef X86SUBTARGET_H
 #define X86SUBTARGET_H
 
+#include "llvm/CallingConv.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Target/TargetSubtargetInfo.h"
-#include "llvm/CallingConv.h"
 #include <string>
 
 #define GET_SUBTARGETINFO_HEADER