Remove buildfiles: second copy of SDL for Mac specific to dev/git builds, and related workarounds for old DP Mac users will need a newer version which can be installed from homebrew as mentioned in https://gitlab.com/xonotic/darkplaces/-/blob/master/README.md#macos
Revert "Update Windows 32 bit SDL build dependency to 2.0.10" This reverts commit d2cdd999d3d7214b2da17099df63b3b409b0ae23.
Upgrade to SDL 2.0.5.
Update Mac OS X SDL framework to 2.0.4
Upgrade to SDL2 on OS X too.