SDL2 Begins Landing More Workable RISC OS Support

Back in February 2020 SDL2 began seeing early work for RISC OS support. Now being merged this weekend to this key library used by many cross-platform games is now more functioning support for the RISC OS Arm-based operating system.

Last year was just the basic support for building SDL2 on Arm OS while merged overnight was keyboard input support, a barebones RISC OS video driver, mode-switching support for RISC OS, and also mouse input support. It's more functioning support for the Simple DirectMedia Layer 2 code to actually be somewhat useful now on RISC OS should any games or other software want to also target that platform.

See these commits for more details on the newly-merged RISC OS SDL2 code.

This documentation was added for SDL2 on RISC OS. RISC OS 3.5+ is supported and needing SharedUnixLibrary, DigitalRenderer, and Iconv as dependencies. SDL2 is working on the operating system for full-screen video output but not yet any windowed mode support, only software rendering is working, and other basics in place except for any joystick/locale/power API support.