[Ohrrpgce] SVN: teeemcee/12371 Fix game window created too large on multimonitor X11. Fixed only with g

[subversion at HamsterRepublic.com]

teeemcee
2021-09-06 06:33:05 -0700 (Mon, 06 Sep 2021)
472
Fix game window created too large on multimonitor X11. Fixed only with gfx_sdl2

The problem was that os_get_screen_size returned size of the whole desktop
rather than the main monitor so some percentage of that could be huge.

When using gfx_sdl2, use SDL2 functions to get the size.

I also wrote some code that queries X11 extension Xinerama to fix this bug
without gfx_sdl2, but it adds a dependency on libXinerama so I left it
commented. Even SDL2 can run without it.
---
U   wip/allmodex.bas
U   wip/os_unix_wm.c
U   wip/whatsnew.txt