libffi-dev should be libffi-devel

Signed-off-by: David Scott <dave.scott@citrix.com>
xcp-networkd: add the manpage

Signed-off-by: David Scott <dave.scott@citrix.com>
Build libnl3 by default

If a distro has it, then it should be placed in the per-distro
exclude file.

Signed-off-by: David Scott <dave.scott@citrix.com>