Shuffle things around in preparation for integrating Eli's constant evaluator.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@53074 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 58dadb0..de0c740 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -13,6 +13,7 @@
 
 #include "clang/AST/ExprObjC.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/APValue.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/TargetInfo.h"