Add default puff type to GMI

Also, change all DOOM games to use CONBACK_DEFAULT, and eliminate now
unused consoleBackOR in missioninfo.
Optional mobjinfo_t *puff param for P_LineAttack

If non-null, will trigger custom puff behaviors.
Merge commit '6dc68dc5ba815c3c82201742ab07f2f07f2d8c88' into AutoDoom
* Replaced pvsnprintf with built-in vsnprintf in B_Log. pvsnprintf was incomplete
* Formatting cleanup
Partial commit of lineeffect module and changes done to p_spec to support that