First of several cleanups to soft dependency implementation.
Convert three functions exported from ffs_softdep.c to static
functions as they are not used outside of ffs_softdep.c.

No functional change.

Tested by:    Peter Holm and Scott Long
Sponsored by: Netflix
popen(): Try to prevent inappropriate fd passing even if 'e' is not used.

Even though not all race conditions can be fixed if the 'e' option is not
used, still fix some race conditions using pipe2():

* Prevent both ends of the pipe from leaking to a concurrent popen().

* Prevent the child process's end of the pipe from leaking to any concurrent
  fork and exec.

This change also simplifies the code.
Second of several cleanups to soft dependency implementation.
Delete two unused functions in ffs_sofdep.c.

No functional change.

Tested by:    Peter Holm and Scott Long
Sponsored by: Netflix
Switch to using the standard uart console driver instead of the special
driver for early boot debugging.
syslog: Use SOCK_CLOEXEC instead of separate fcntl() call.
Add a driver for the Freescale Fast Ethernet Controller found on various
Freescale SoCs including the i.MX series.  This also works for the newer
SoCs with the ENET gigabit controller, but doesn't use any of the new
hardware features other than enabling gigabit speed.
Third of several cleanups to soft dependency implementation.
Ensure that softdep_unmount() and softdep_setup_sbupdate()
only get called for filesystems running with soft dependencies.

No functional change.

Tested by:    Peter Holm and Scott Long
Sponsored by: Netflix