- Display the available build knobs via a pre-everything target.
- Remove the autodetection for X11 support and the WITH_X11 knob, instead
always build with X11 support and add a WITHOUT_X11 knob. Together with
an additional ssh2-nox11 slave port this allows easier handling of these
two variants and to have pre-compiled packages for both (ssh2 with X11
support depends on X11 libraries).
Submitted by: maintainer (marius)