DO NOT MERGE THIS INTO THE INTERNAL REPO. This is a temporary 2.1.15 only fix. This commit allows an optional boolean for tan(), which when true will automatically shift angles by ANGLE_90.
The point here is ColorOpposite(MAXSKINCOLORS) would have given an actual result of its own since MAXSKINCOLORS & MAXSKINCOLORS is still MAXSKINCOLORS. This shouldn't happen though, as both Color_Opposite[MAXSKINCOLORS*2] and Color_Opposite[MAXSKINCOLOR*2+1] aren't defined.
Angles now go from 0 to 0xFFFF (360 degrees == FRACUNIT) instead
of using a full UINT32. Lua only has one number type, so signedness
gets in the way of using angle_t directly. This handling of angles
matches up with how ZDoom ACS scripting and the like does it.
I also changed all the integer casts and pushes of fixed_t to
their own macro in preperation for possible future seperation.
