merge a bit of duplicated code.
dedup and add the drmkms modules
add the drmkms modules
enable awinhdmi, awintcon, awindebe, genfb, wsmux, wsfont and
with VCONS_DRAW_INTR
Just _GNU_SOURCE should be enough to expose everything necessary on Linux
work around c11 visibility problems on some version(s) of FreeBSD