Speed-optimize Denise::translate()

[dirkwhoffmann]

Findings after a brief code review:

• At the end of Denise::translate(), the contents of iBuffer and mBuffer are identical (the mBuffer is modified later in drawSprites()).
• The iBuffer is only needed in lines with HAM mode enabled.

Optimization:

• At the end of Denise::translate(), check if this line is a HAM line. If yes, create the iBuffer by duplicating the mBuffer. Otherwise, go without the iBuffer.

[dirkwhoffmann]

Speed comparison (Kick 1.3, hand & disk boot screen):

Upper: Latest dev-branch (frame skipping, audio fast path, on-demand-iBuffer): Lower: vAmiga 2.5