ipc.c: Use standard POSIX error codes instead of Linux centric ones.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
configure: net/route.h needs sys/socket.h on FreeBSD

FreeBSD fixes
- net/route.h needs sys/socket.h (struct sockaddr)
- netinet/ip_mroute.h needs sys/types.h (u_long et consortes)

Fixes part of smcroute issue #5

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
Makefile.in: Cleanup and refactor dep file generation on behalf of FreeBSD

- Refactor dep file generation using fancy new GCC feature
- Remove ifneq's around -include, not needed now

Fixes part of smcroute issue #5

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
mroute-api.c: Misc. build fixes for FreeBSD

- Fix comment-within-comment Linux/*BSD --> Linux and *BSD
- Fix 'struct vif' definition --> struct { .. } vif_list[]

Fixes part of smcroute issue #5

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
smcroute.c: Fix build errors on FreeBSD

The System V calling convention for setpgrp() is not available on
FreeBSD, replace with equivalent setpgid(0, 0).

Also, fix missing return value in read_mroute6_socket().

Fixes part of smcroute issue #5

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