.lit files and duplicate map names

[qbism]

/any_mod/maps/start.bsp will find /id/maps/start.lit and load the sucker, if it doesn't have it's own .lit. Not pretty.
This can happen for any maps with duplicate names. A lot of mods have custom start maps, so that's probably the most common.

Fix options:
1. Check that the absolute paths of the .bsp and .lit match. A bit of work, model_t only stores relative paths.
2. Compare .lit file size to lightdata (the standard lighting). The .lit file size is lightdata * 3 + 8. Doubles as an integrity check.

Similar 'add-on' files types like .ent may have the same issue.

[leileilol]

[mh]

I've been doing option 2 almost since time began; it works, it's fast and easy, and there's no messy code involved.

Option 1 will break if the LIT file is intended to be valid (e.g. LIT files for id1 in a gamedir). Highly unlikely, but it's still a break case.