Only unmount non-protected filesystems at shutdown

This patch adds support for a more fine grained approach to what
filesystems are unmounted at shutdown/reboot.  This so we later
can add support for `mdadm --wait-clean --scan`, which relies on
/proc, /sys, and /dev being there before we call reboot().

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

Makefile.am

@@ -1,8 +1,8 @@
 ACLOCAL_AMFLAGS    = -I m4
 sbin_PROGRAMS      = finit initctl reboot
-finit_SOURCES      = finit.c api.c client.c conf.c exec.c getty.c helpers.c pid.c \
-		     sig.c svc.c service.c plugin.c tty.c cond.c cond-w.c sm.c    \
-		     utmp-api.c utmp-api.h
+finit_SOURCES      = finit.c api.c client.c conf.c exec.c getty.c helpers.c \
+		     mount.c pid.c sig.c svc.c service.c plugin.c tty.c	    \
+		     cond.c cond-w.c sm.c utmp-api.c utmp-api.h
 pkginclude_HEADERS = cond.h finit.h helpers.h inetd.h plugin.h svc.h
 if INETD
 finit_SOURCES     += inetd.c