Significant change of Signal behavior

Signals, now instead of being a single type with 1 generic argument, now
come in four flavors, each with an added argument count, starting at
Signal which takes *no* arguments (this will probably cause trouble in
legacy code).

A bit miffed that I couldn't figure out a way to do variable number of
arguments via abstract or somesuch. Maybe there's still a way using @:to
?
Vector cross product and Ray intersection
Signal updates, Flash compat
More Flash compat + minor stuff