[0.16, 0.17] Alt remapped to Scroll Lock counts twice

[Lorash]

Repro steps:
* Rebind "Show Info" from Alt to Scroll Lock
* Press Scroll Lock but don't release: counts as button press 1
* Release Scroll Lock: counts as button press 2

I actually like this because it lets me stay in alt mode forever, but I guess it's technically a bug. Happens on 0.16 and 0.17.

[posila]

Thanks for the report.
Fixed for 0.17.24.

I am not sure why it didn't work in 0.16; I found a code that was supposed to workaround ScrollLock not emitting key-down event, but with SDL we do receive the event, so the workaround was generating extra action.