Introducing full desktop GL support for Mir servers (LP: #1420581)
It works well with Mesa, but is disabled by default due to one remaining "TODO" you will find.
Note the new eglBindAPI calls. Without those, EGL makes all new threads default to ES. And then eglMakeContext/eglGetCurrent* functions will randomly fail. So we need to be sure any thread that touches EGL will call eglBindAPI with the correct value first. Fixes: https://bugs.launchpad.net/bugs/1420581.