This backports some changes to #319 to fix the screenshooter data
format. This also adds wlr_backend_get_renderer which will be
useful to support multiple renderers.
* Moved os-compatibility.c to util
* Added header under util
* Removed static since it isn't needed (i think so)
* Adjusted meson.build to include lib_wlr
Improved some codestyle
* Added guard to os-compatibility.h
* Fixed typo in include statment
Adjusted Guard
* Changed guard to _WLR_UTIL_OS_COMPATIBILITY
emersion
Johannes Schramm
Timidger
Drew DeVault
Dominique Martinet
Moritz
Tancredi Orlando