[NFC] Header cleanup

Summary: Removed unused headers, replaced some headers with forward class declarations

Patch by: Eugene <claprix@yandex.ru>

Differential Revision: https://reviews.llvm.org/D20100

llvm-svn: 275882
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 23d1854..50c5385 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -11,7 +11,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "clang/Serialization/ASTWriter.h"
 #include "ASTCommon.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclContextInternals.h"
@@ -20,7 +19,7 @@
 #include "clang/AST/Expr.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Serialization/ASTReader.h"
-#include "llvm/ADT/Twine.h"
+#include "clang/Serialization/ASTWriter.h"
 #include "llvm/Bitcode/BitstreamWriter.h"
 #include "llvm/Support/ErrorHandling.h"
 using namespace clang;