Two-ways signals

[Nazalassa]

Makes it possible for trains to ignore some signals when they go in the opposite direction, rather than blocking them. This could be useful at junctions, or on single-tracked lines (e.g choose signal at the end). Each signal can do either this or the default behaviour through a new checkbox in the signal info window.

Examples:
 

[poppo]

Interesting .
I'd like to ask a few questions and make some suggestions (just my personal opinion).

• How does a signal behave when placed on a railroad switch? And can we edit the signal-running direction on the railroad switch?
• Is a choose signal of the opposite direction placed after a choose signal found in route_t::find_route()? (It should not be.)
• Is it possible to place different signals on the opposite sides of the same tile?
  (I know that current signal system doesn't allow this. But I think it would be more useful if, on a single-track line, one direction could be set to "choose" while the other could be set to "longblock" or "pre-signal".)