Fix wall transfer cap for slopes with angles beyond the first quadrant

Resolves #1335 (closed). It appears wall transfers are intended to give a 15° buff to the slope angle, with a cap at 90°/270°. The root issue is that slope->zangle > 0 is never false because angles are unsigned (perhaps the function author was in the Lua brainspace), so a slope that faces away from a wall and inclines downwards accidentally gets a 15° nerf instead of a 15° buff. The condition for applying the cap is also incorrect; it ignores that slope angles approaching 90°/270° can do so from any of the four quadrants.

Could break some maps built around the weaker wall launches?

approved this merge request

added Bug Changed behavior Movement/physics labels

changed milestone to %2.2.15

changed milestone to %2.2.16

added 202 commits

• 1152c8c4...8701ef41 - 201 commits from branch STJr:next
• 5162772d - Merge branch SRB2:next into fix-1335

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merged

mentioned in commit 692971d7