Teach PackExpansionExpr to keep track of the number of pack expansions
it will expand to, if known. Propagate this information throughout Sema.

llvm-svn: 123470
diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
index b0a1e4e..022b619 100644
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -1294,6 +1294,7 @@
 void ASTStmtReader::VisitPackExpansionExpr(PackExpansionExpr *E) {
   VisitExpr(E);
   E->EllipsisLoc = ReadSourceLocation(Record, Idx);
+  E->NumExpansions = Record[Idx++];
   E->Pattern = Reader.ReadSubExpr();  
 }