Previously, actor[].shootzvel (implementation detail, not available to CON)
was checked, and if it was !=0, that was the overridden velocity. The value
0 meant "hardcoded, projectile-dependent velocity". But that neccesiated a
hack where if zvel 0 was passed and really meant, it needed to be set to
1 instead. Now we have A_ShootWithZvel() taking an additional last argument
plus a macro SHOOT_HARDCODED_ZVEL permissible for that argument.
git-svn-id: https://svn.eduke32.com/eduke32@3465 1a8010ca-5511-0410-912e-c29ae57300e0
