Trams not filtered

[Václav]

In vehicle list, vehicle type trams is not allowed to be filtered.

I have some trams in game. I sent some ones into depot - but I did not know to which depot they went.
I wanted to see (in vehicle list) only trams - but no one was showed.
I used some other (special) filters - but they run only alone or with else vehicle types. In all cases no tram is showed.

[prissi]

Trams are inteally trains for most purposes. This is rather an extension request (and a quite reasonable one).

[Václav]

But they are not showed also in group of trains, too.

[Dwachs]

This is a bug. The filtering is still broken.

Edit: It seems that the enum flags in convoi_filter_frame_t are limited to 16 bits, and thus break some filter buttons.

Edit2: Fixed with r6066.