Alias loop causes endless JS loop

[egmontkob]

Apply a skin that has an endless alias loop, like

[aliases]
    a = b
    b = a

This results in a busy-JS-looping page, hopefully the browser intervening and stopping it soon.

Here's how mc detects loops, something like this should be done by our JS code too: https://github.com/MidnightCommander/mc/blob/4.8.33/lib/skin/colors.c#L157