Macro history (de-)serialization. Deserialization currently reads only the latest macro definition. Needs more work.

Summary: Passes all tests (+ the new one with code completion), but needs a thorough review in part related to modules.

Reviewers: doug.gregor

Reviewed By: alexfh

CC: cfe-commits, rsmith

Differential Revision: http://llvm-reviews.chandlerc.com/D41

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@164610 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Basic/IdentifierTable.cpp b/lib/Basic/IdentifierTable.cpp
index 082c768..55c45cf 100644
--- a/lib/Basic/IdentifierTable.cpp
+++ b/lib/Basic/IdentifierTable.cpp
@@ -33,6 +33,7 @@
   TokenID = tok::identifier;
   ObjCOrBuiltinID = 0;
   HasMacro = false;
+  HadMacro = false;
   IsExtension = false;
   IsCXX11CompatKeyword = false;
   IsPoisoned = false;