Raise MAX_ENT_LEAFS from 16 to 32, fixes disappearing/flickering bmodels in some situations. In particular fixes an elevator in fort_driant-fullvis.bsp, and a grate (func_door) in jam1_ionous.bsp.

From what I understand, if an entity touches more than MAX_ENT_LEAFS, it will only be visible
if the player happens to be standing in one of the first 'MAX_ENT_LEAFS' (so essentially random).

See discussion of MAX_ENT_LEAFS here:
http://celephais.net/board/view_thread.php?id=60310

For more detail (mh has an alternate fix, used in DirectQ/RMQEngine, haven't looked in to what he did):
http://forums.inside3d.com/viewtopic.php?t=2376&postdays=0&postorder=asc&start=23

git-svn-id: svn://svn.code.sf.net/p/quakespasm/code/trunk@967 af15c1b1-3010-417e-b628-4374ebc0bcbd