x11-toolkits/Xaw3d: Assume maintainership

Assume maintainership because I have plans for this port.

libXaw3d is now maintained by the freedesktop.org project. The plan is
to:

1. Rename this port to x11-toolkits/libXaw3d.
2. Update the port to 1.6.6 as per

https://gitlab.freedesktop.org/xorg/lib/libxaw3d.
This passes the build test.

3. Update dependent ports to the new origin.
4. Exp-run.
5. Finally push the updated libXaw3d.