[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/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 47d1326..c71e270 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -21,15 +21,14 @@
 ///
 //===----------------------------------------------------------------------===//
 
-#include "clang/Parse/Parser.h"
 #include "RAIIObjectsForParser.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/Basic/PrettyStackTrace.h"
+#include "clang/Parse/Parser.h"
 #include "clang/Sema/DeclSpec.h"
 #include "clang/Sema/ParsedTemplate.h"
 #include "clang/Sema/Scope.h"
 #include "clang/Sema/TypoCorrection.h"
-#include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 using namespace clang;