ESC/P 2: 4 versions, filtering by version, selectable paper.

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.

src/include/86box/prt_papersizes.h

@@ -47,4 +47,8 @@
 #define A4_PAGE_WIDTH   8.25
 #define A4_PAGE_HEIGHT  11.75
 
+/* Standard B4 */
+#define B4_PAGE_WIDTH   9.875
+#define B4_PAGE_HEIGHT  13.875
+
 #endif /*EMU_PLAT_FALLTHROUGH_H*/