It looks like HSER_BITS 9 was added when the HSEROUT2 and HSERIN2 commands (along with the HSER2_BITS define) were added.

I'll pull a PIC out with 2 USARTS and test both HSEROUT and HSEROUT2 later when I've some free time.

You can of course BYPASS the HSEROUT defines and set-up the PIC's registers manually...