Fix serialization/deserialization for __uuidof

I broke this back in r264529 because I forgot to serialize the UuidAttr
member.  Fix this by replacing the UuidAttr with a StringRef which is
properly serialized and deserialized.

llvm-svn: 264562
diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
index c2256eb..f8fb2b8 100644
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -1680,6 +1680,8 @@
 void ASTStmtReader::VisitCXXUuidofExpr(CXXUuidofExpr *E) {
   VisitExpr(E);
   E->setSourceRange(ReadSourceRange(Record, Idx));
+  std::string UuidStr = ReadString(Record, Idx);
+  E->setUuidStr(StringRef(UuidStr).copy(Reader.getContext()));
   if (E->isTypeOperand()) { // __uuidof(ComType)
     E->setTypeOperandSourceInfo(
         GetTypeSourceInfo(Record, Idx));