Sneak glitch: Detect ledge for 2-node climb-up

Sneak glitch: Detect ledge for 2-node climb-up

Re-creates the old sneak-jump behaviour in new code.
Enabled by the 'sneak glitch' physics override.
When a ledge is detected the jump speed modifier is set to the larger
of 'physics override jump' and 1.3 to allow a 2-node climb-up.

An unexpected side-effect is the simple sneak ladder working smoothly.