Avoid Attr.h includes, CodeGen edition

This saves around 20 includes of Attr.h. Not much.
diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index 6f3d6d8..8369fc2 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -16,9 +16,10 @@
 #include "CodeGenModule.h"
 #include "TargetInfo.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/Attr.h"
+#include "clang/AST/DeclOpenMP.h"
 #include "clang/AST/Stmt.h"
 #include "clang/AST/StmtOpenMP.h"
-#include "clang/AST/DeclOpenMP.h"
 #include "clang/Basic/PrettyStackTrace.h"
 using namespace clang;
 using namespace CodeGen;