Also catch other possible macro names for track forward/back buttons

On a keyboard I have (and possibly on the actual laptop keys itself), the standard track forward/backward buttons don't do anything.  I traced this to the fact that they're emitting key press events as `NX_KEYTYPE_NEXT`/`NX_KEYTYPE_PREVIOUS ` instead of `NX_KEYTYPE_FAST`/`NX_KEYTYPE_PREVIOUS`.  So this PR just adds those to the possible key codes that are caught and treated as forward/backward tracks.