Add the ability for staticroute to evaluate lines from /etc/route.conf
as shell script fragments, add example to the route.conf man page of
evaluating variables.

Remove route.conf man page statement that staticroute is enabled in
rc.conf since that's incorrect.

Wrap the staticroute while in parens, per <apb> & <christos>, and
quote all the arguments for the evals.

branches: 1.5.6; 1.5.8;
Add proper error reporting via the return code:
Remember if any of the "route" commands failed and return an error in
that case.

Add a "return 0" to avoid incorrect error returns because we ran out of
lines to read from "/etc/route.conf".

branches: 1.3.2; 1.3.12;
Add comment to point to manual page for details.

branches: 1.2.16;
Add an _rc_subr_loaded variable, set to ":" by rc.subr. Scripts can use this
for a speedup by doing:
$_rc_subr_loaded . /etc/rc.subr

Script to add and remove static routes:

eg:
$ cat /etc/route.conf
# Turn on/off IP forwarding.
+sysctl -w net.inet.ip.forwarding=1
-sysctl -w net.inet.ip.forwarding=0
net 192.168.2.0 -netmask 255.255.255.0 192.168.150.2