Sort all of Clang's files under 'lib', and fix up the broken headers
uncovered.

This required manually correcting all of the incorrect main-module
headers I could find, and running the new llvm/utils/sort_includes.py
script over the files.

I also manually added quite a few missing headers that were uncovered by
shuffling the order or moving headers up to be main-module-headers.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169237 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/DeclGroup.cpp b/lib/AST/DeclGroup.cpp
index 036acc2..9861f22 100644
--- a/lib/AST/DeclGroup.cpp
+++ b/lib/AST/DeclGroup.cpp
@@ -12,8 +12,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/AST/DeclGroup.h"
-#include "clang/AST/Decl.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/Decl.h"
 #include "llvm/Support/Allocator.h"
 using namespace clang;