try implementing fetching cards from RAM when required.
begin to add machinery for more VIC-II like fetching of screen ram
data.  We will fetch in the horitzontal front porch of every physical
raster, but only change the address we fetch from when changing
character rows.
add FIFO for screen ram to hooks added previously.
add VHDL files for screen ram fifo.
fix width of expression.
fix width of expression in another spot
more rom annotations.
more ROM annotations (including all $FF7D printed messages).
try using screen ram fifo as source of characters.
fix bugs in badline fetching.
reverse byte order when loading FIFO.
work towards custom character sets and bitmap data.
fix type casting of expression.
replace FIFO with lower-latency variant so that bitmap data etc
can be fetched within 8 cycles with 16-bit character set.
try to fix vertical out by one for screen data.
fix duplicated first row of characters.
improve previous commit to reduce logic depth.
prime read side of screen ram fifo.
fix typo in priming of screen ram fifo.
improve character video generator to simplify, and hopefully make
proper use of RAM for custom character sets.
fix bugs with determining when to read from character set rom.