[Ohrrpgce] SVN: teeemcee/12427 Remove support for SDL 2.0.3; Linux release builds now require 2.0.5

[subversion at HamsterRepublic.com]

teeemcee
2021-09-12 04:45:18 -0700 (Sun, 12 Sep 2021)
826
Remove support for SDL 2.0.3; Linux release builds now require 2.0.5

The .deb dependencies already included 2.0.5+ anyway.

As a result of this change, in linux release builds:
-mouse drags over the window edge are fixed
-changing the resizable state of the window (e.g. when entering an in-game
 debug menu) no longer causes massive flickering and window recentering due to
 recreating the window, which was especially bad when fullscreen.
 (The recentering happened regardless of the previous commit which fixed
 recentering in general.)
-unplugging and replugging a joystick no longer works, but on the other hand
 this fixes the massive lag that accompanied it

Plus it's much less confusing for linux builds to behave the same as Windows/Mac
ones.

This removes "scons sdl203=1" flag.

(Copied from r12420 on wip branch)
---
U   rel/hrodvitnir/SConscript
U   rel/hrodvitnir/gfx_sdl2.bas
U   rel/hrodvitnir/gfx_sdl_common.bas