routesock.c: Retry routing socket on EAGAIN after one second sleep.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
Join/Leave multicast group 224.0.0.13 (All PIM Routers) on correct socket

This commit changes on which socket pimd joins the multicast group
224.0.0.13, the all PIM routers group.  On a Linux kernel it does not
seem to matter which socket is used, but on FreeBSD, and possibly other
UNIX kernels, this does not work.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
config.mk: Note that pimd has been verified on FreeBSD 9.x

- Minor cleanup
- Move Linux definition first, is after all the primary platform
- Remove FreeBSD 2.x definition
- Replace FreeBSD 3.x/4.x with verified on FreeBSD 9.x

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>