Implements the ?. operator, replacing code like A && A.B with A?.B
BYOND Ref:
When reading A?.B, it's equivalent to A && A.B except that A is only evaluated once, even if it's a complex expression like a proc call.
* Makes plastitanium windows children of reinforced windows.
* Unanchored variety isn't fully tooled in now.
* Path moved to plasma/reinforced/plastitanium
* Fixes a blunder about neglecting a mapping path change.