add build target for videoproxy
add message on exit
work towards variable numbers of character rows in unicode text
output.
move screen ram to $3800, to allow for 16 rows of characters, and
hence 128-pixel high text.
12 character rows for above the baseline, and 4 for below the
base line, so 96 pixels above, 32 below.
only print character rows that have something in them.
working on filtering out empty rows
exclude blank rows of characters from output.
fix lots of bugs relating to drawing rows of characters.
only draw relevant character rows
(underhang rows get drawn, but have garbage)
fix bugs with glyphs with underhangs.
pull in updated font that has glyph tile rows in correct order.
use blank tile to fill in gaps in output.