bad loop

[Shpoike]

https://github.com/sezero/quakespasm/blob/master/Quake/r_world.c#L131 by pre-skipping leaf 0 (as required by pvs), that array reads 1 leaf and 1 pvsbit beyond the end of their respective arrays, which could result in bad reads or even writes.

[sezero]

Do you have a patch?

CC: @andrei-drexler, @ericwa