Draft: Increase maximum unlockables
Based on !1749, since this also requires changes to gamedata.
- Increases MAXUNLOCKABLES from 32 to 80.
- Increases MAXEXTRAEMBLEMS from 16 to 48.
- These two now add up to 128, which is equal to MAXCONDITIONSETS.
- NOTE: Because of the way unlockable skins are set up, it's not possible to have more than 32 of them at the moment.
- Fixes linedef actions 319 and 320.
First implemented and tested this based on next, and was about to push it... and then I remembered !1749 already changes how gamedata is handled, so I figured it'd be easier to build it off of those changes.
Closes #770.