The four versions are:
- EX-1000 and 7 other early printers (including FX-80, the only Epson
available OOTB for Windows 1.03), have ESC i and ESC j.
- 9-pin ESC/P, a superset of EX-1000 besides ESC i and ESC j.
- 24-pin ESC/P in 360 DPI instead of 240.
- ESC/P 2 with raster graphics.
As for paper, four sizes: Letter, A4, Legal, B4. The former ones are
mainly for EX-800, the latter two are sideways and meant for EX-1000.
I did some other minor changes, like converting a bunch of defines to enum.
