build fix

Some warnings are now treated as errors, bring the less-visited parts
of the source code up to date.
driver: texture alignment, preparation for multi-pipe

Correct texture and RS alignment.
For multi-tiled and multi-super-tiled surfaces (for multiple pixel
pipes) a special texture format is used.
driver: PA_LINE_WIDTH contains the half width

Divide the line width by two to correct line rendering.
Also update documentation.
driver: proper flushing of TS

RS_FLUSH seems to be TS_FLUSH -- ie, the TS_FLUSH command flushes
the internal cache of the tile status. It needs to be invoked after a
manual clear of the TS.
This solves a few corruption and (esp. blockyness) issues.