FastSerializerHelper::singleElement/startElement internal API changed
This is just to notify those who might currently use
FastSerializerHelper in patches being prepared.
Commit 1fe24bb1e2fbe44a4bf2c03297e259b3a18b1235 has modified the
singleElement/startElement[NS] APIs by removing FSEND (which was a
remnant of old C-style varargs implementation). So if you use these APIs
in your ongoing work, please rebase.