move exit(3) to plan9.h, choose between threadexitsall and exits depending on __plan9_keep_main__
make "main" function overriding optional
link the guide in the readme
limits: increase PATH_MAX to 4096
getenv: map XDG_* and USER variables to something
relax includes. again.
move custom getenv into the main header
SDL_RenderCopy: fall back to memimagedraw if no stretching done
rearrange and rename to avoid conflicts
sdl2: mouse: support middle button
add sigaction
update readme
build & install as syslibs
dump it to git so I do not lose anything