xev ouput for the right ALT key (updated):

KeyRelease event, serial 37, synthetic NO, window 0x4400001,
    root 0x170, subw 0x0, time 497630, (45,-8), root:(676,349),
    state 0x88, keycode 108 (keysym 0xfe03, ISO_Level3_Shift), same_screen YES,
    XKeysymToKeycode returns keycode: 64
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False