Add support for Simple Direct Layer (media library)

Packages describing “sdl” as local USE flag

Package“sdl” Flag Description
app-emulation/qemuEnable the SDL-based console
app-emulation/wine-protonEnable gamepad support using media-libs/libsdl2
app-emulation/wine-stagingEnable gamepad support using media-libs/libsdl2
app-emulation/wine-vanillaEnable gamepad support using media-libs/libsdl2
dev-util/sdl-jstestEnable media-libs/libsdl2 based input test
media-libs/libde265Enable video output of dec265 example program with media-libs/libsdl
media-libs/quircBuild tools requiring media-libs/sdl-gfx (inspect, quirc-demo)
media-video/mpvEnable media-libs/libsdl2 based video and audio outputs (Note: these outputs exist for compatibility reasons only, avoid if possible)
sci-libs/vtkEnable SDL2 support for rendering modules
x11-libs/wxGTKUse Simple Directmedia Layer (media-libs/libsdl) for audio.

All packages providing a “sdl” USE flag (66)