always_run flag for terrain

[igroglaz]

If we use such terrains as walls in dungeon.txt:

name:obj_grass L ruins
graphics:::s
priority:18
flags:LOS | PROJECT | PASSABLE | TORCH | BORING

They prevent running. It will be fun to have special flag 'RUN' which will allow running nearby to that terrain without pause :)

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[14:58] PowerWyrm: it existed before (option "run past corners") but got removed
[14:59] PowerWyrm: but yeah could be an option -- don't make adjacent features stop running