- properly clip glyphs drawn into off-screen memory
- when drawing glyphs skip pixels with zero alpha

Fix the build. Commented out code that is missing #defines

use the hardware to draw anti-aliased text
visible speedup
The problem is that HP didn't implement full alpha blending support on the FX4,
just what's needed to draw anti-aliased lines and edges, and no upper byte in
32bit buffers, which means we can't have anything with alpha in video memory
but we can apply alpha blending when scribbling into video memory using BINC,
therefore we do *not* want out glyph sources in VRAM...

adjust FIFO slots in SummitWaitFifo() calls

some updates:
- turn pixel processing off for GXcopy - small speedup
- remove unnecessary exaMarkSync() calls
- set prefetch hint in SummitDownloadFromScreen() - *big* speedup

some udates:
- don't use hwmode, just track read- and write mode directly
- use FIFO pacing now that we know how, only stall the engine if we need to
access video memory or change buffer access modes
- use a back buffer as off-screen memory, modify Prepare*() etc. accordingly

use ROPs now that we know how

support 24bit

add *very* experimental Visualize FX support