MINIMAL: remove debugging and some loadable network modules

Remove deugging stuff, since it's arguably not needed in a minimal
setup. Also vlan, tuntap and gif since they can be loaded.

imp didn't include the part of the patch that removed xen guest support.
Xen guest is relatively small and has no way of being loaded.

Reviewed by: imp
PR: 229564
MFC After: 3 days