drirc: Enable glthread for melonDS
Inspired by the dolphin/citra/yuzu change. In Fire Emblem Shadow Dragon, in the last stage, it went from 220-230FPS to 230-240FPS, by setting mesa_glthread. The test was done on a i7 4790K with a 580X.
Signed-off-by: John Ettedgui john.ettedgui@gmail.com