Ensure make -j N universe works correctly, by checking for an up-to-date
make before starting the universe targets themselves.  Otherwise, all of
the targets would attempt to build make simultaneously, overwriting each
other's copies of the make object files and executable.  This could lead
to strange errors, for example when partially-written make executables
are invoked.

Also amend r216620, to make the rest of universe wait properly until the
upgrade_checks target is finished, by adding universe_${target}_prologue
to the .ORDER target.  Otherwise, make will be too smart for its own
good, and start building the universe targets simultaneously with the
prologues anyway.

MFC after:	1 week
Fix a race condition on tcp listen socket teardown with pending
connections in the accept queue and contiguous new incoming SYNs.

Compared to the original submitters patch I've moved the test
next to the SYN handling to have it together in a logical unit
and reworded the comment explaining the issue.

Submitted by:	Matt Miller <matt@matthewjmiller.net>
Submitted by:	Juan Mojica <jmojica@gmail.com>
Reviewed by:	Matt Miller (changes)
Tested by:	pho
MFC after:	1 week
Change certain heavily used network related mutexes and rwlocks to
reside on their own cache line to prevent false sharing with other
nearby structures, especially for those in the .bss segment.

NB: Those mutexes and rwlocks with variables next to them that get
changed on every invocation do not benefit from their own cache line.
Actually it may be net negative because two cache misses would be
incurred in those cases.