Fix UDMF FOF flags
This fixes the bugs that were introduced by rearranging the FOF flags for UDMF. In particular:
- The flags for custom FOFs (linedef type 259) are now set properly.
- I added a backwards compatibility layer to ensure that old Lua scripts still work correctly. This required renaming
ffloor_t::flagstoffloor_t::fofflagsand all theFF_constants toFOF_. Which is kind of annoying, but I didn't see any way around it.flagsand the oldFF_constants are still exposed to Lua, and if you use them, the game will do all the necessary conversion in the background. New scripts should usefofflagsand theFOF_constants for regular flags,bustflagsand theFB_constants for the bustable FOF flags, andbusttypeand theBT_constants for the bustable FOF type.