Remove Software tricks

/// \file
/// \brief special trick routines to make some SW tricks look OK with
///	HW rendering. This includes:
///	- deepwatereffect (e.g. tnt/map02)
///	- invisible staircase (e.g. eternal/map02)
///	- floating ceilings (e.g. eternal/map03)
///
///	It is not guaranteed that it looks identical to the SW mode,
///	but it looks in most of the cases far better than having
///	holes in the architecture, HOM, etc.

hw_trick.c is a file that attempts to recreate vanilla Doom mapping exploits, such as the deep water trick, and invisible staircases (see testholes.wad, enable gr_correcttricks.) Those effects are not relevant in the context of SRB2, and usually breaks some maps (sometimes with intended effects) when enabled. This branch removes hw_trick.c and the corresponding console variable.