[Ohrrpgce] SVN: teeemcee/12186 gfx_sdl2: when the zoom changes update the minimum window size

[subversion at HamsterRepublic.com]

teeemcee
2021-01-19 19:11:13 -0800 (Tue, 19 Jan 2021)
183
gfx_sdl2: when the zoom changes update the minimum window size

Also try to clarify the existing code.

(gfx_sdl2 is the only backend that actually supports setting a min window size)
---
U   wip/common.rbas
U   wip/gfx.bi
U   wip/gfx_sdl2.bas