Ignore event spams of keys we already have

A key press should only cause a state change if the key wasn't pressed
before.
Add missing range-check in hotkey_dag_get_next()
Check whether interested in release event before processing it

This saves us a little bit of overhead.
It also prevents waysome from producing a deceptive log messge.
Merge pull request #513 from neithernut/add-hotkeys-ignore_multiple_presses

Ignore event spams of keys we already have