Add EGL framework. Rename fbuf to display

For now the only available display will be the default display, acquired
by calling eglGetDisplay(EGL_DEFAULT_DISPLAY). All other values will
return EGL_NO_DISPLAY. The only available configuration will be the default
display's current configuration. This is done because phi doesn't have a
window manager, so EGL will only have access to the default (native) display.

Renamed fbuf to display. Will likely cange some API function names as well.