Add additional evdev key mappings for multimedia and Korean keyboards

This patch adds key definitions for the following:
* Hangul/Hanja keys on the Korean keyboard (on either side of the spacebar)
* Multimedia keys such as media play, back; volume up/down; browser buttons
* Common aliases of already-defined keys, e.g. NFER for MUHE.

It leaves commented out all the evdev keys for which there appears to be no VK_* equivalent.