Sort all the #include lines with LLVM's utils/sort_includes.py which
encodes the canonical rules for LLVM's style. I noticed this had drifted
quite a bit when cleaning up LLVM, so wanted to clean up Clang as well.

llvm-svn: 198686
diff --git a/clang/lib/AST/DeclOpenMP.cpp b/clang/lib/AST/DeclOpenMP.cpp
index 8f45471..37d4ae2 100644
--- a/clang/lib/AST/DeclOpenMP.cpp
+++ b/clang/lib/AST/DeclOpenMP.cpp
@@ -12,8 +12,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/AST/ASTContext.h"
-#include "clang/AST/DeclBase.h"
 #include "clang/AST/Decl.h"
+#include "clang/AST/DeclBase.h"
 #include "clang/AST/DeclOpenMP.h"
 #include "clang/AST/Expr.h"