Increased the FIFO buffer size to 2MB from 1MB.  Fixes Killer 7's Angel boss.

Fixes issue 5415.
Added direct GameCube controller commands to the Serial Interface emulation.  Fixes the controls in MaxPlay Classic Games Volume 1 and the Action Replay disc.
Enabled Synchronise GPU on "SPEED CHALLENGE - Jacques Villeneuve's Racing Vision".  Required to go in-game.