from mailslot (part of fix for upload to FDSZ).
Bug-fix: don't potentially overwrite the bounds of the rx ring buffer.
Better input_thread debug logging.
Bug-fix: VDD_STATUS could return garbage for input full/size if GetMailslotInfo
fails (which it appears is doing) - which could be an issue for FOSSIL apps
which rely on function 5.
Specify unlimited-size msgs for receive (input) mailslot (part of fix for FDSZ
upload).