P_IsPointInSubsector now works in both Software and GL, which means it can be...

P_IsPointInSubsector now works in both Software and GL, which means it can be used as the main driver behind support for Knuckles climbing on one-sided walls.

Also, the "teleport" devmode command can now gracefully handle coordinates specified outside maps with no/few thok barriers, which previously prevented teleport via the thok barrier bleed's sector floor and ceiling being equal.