changelog:
* Cleaned the gba.cpp code a bit (too much changed to list them).
* Changed all the clockticks management. Internal emulation speed should be more accurate now (fixes some games that crashed, like Advance Wars 2 or Tennis no Oojisama 2003), some other should have less slowdown/flickering (Breath of Fire 3's underwater level, Mario & Luigi Saga's intro). Added pseudo-support for bus prefetch (still need to check how it works for all the cases).
* Added a 3 lines delay between the time a BG is enabled and the time it is displayed on screen (Lady Sia 2's blue lines on water level bug).
* Put the supposed correct settings in DISPSTAT and lcdTicks on bootup when no bios are used (or when bios animation is skipped). (Earthworm Jim 2 now boots up).
* Added a rom mirroring option in the 'Game Override' menu. Enabling it for the 'Mini'/'Classic' series makes the controls respond properly.
* Bit 15 of WAITCNT is now read-only (Donkey Kong King of Swing doesn't crash on some levels anymore).
* Bit 11 and 15 of SGCNT (FIFO Reset bits) are now cleared.
* Corrected a bug introduced in VBA 1.8.0 which would prevent a game from accessing the 0x10000+ area of VRAM (Duke Nukem & Need for Speed 2's flickering is gone).
* Added a 'pseudo-support' for GFX modes 6&7 (but no games should use them).
* Soft Reset is now working properly (it was broken when the prefetch emulation was added).