kernel - Increase IFQ_MAXLEN from 50 to 250

* IFQ_MAXLEN is used as the default for numerous pseudo-network drivers.
  The value 50 is just too low.  Increase to 250.
kernel - Fix several bugs in FAIRQ

* Fix several possible overflows due to high-valued machclk_freq constants
  and uint's that should have been uint64's.  Among other things this fixes
  bandwidth calculations that could previously get into weird states.

* Refactor the fairq_selectq() routine to fix numerous cases where the
  head of the queue could get advanced multiple times without pulling a
  packet off the queue, causing packets in queues to be excessively
  delayed.

Both of these were rather serious issues.  Operation is far smoother with
the bugs fixed.
<sys/cdefs.h>: Add some macros needed for our <tgmath.h>.

Taken-from: FreeBSD
gcc: Stop installing GCC's tgmath.h to /usr/libdata/gcc{44,47}.

Before this commit, the recently imported <tgmath.h> (in
/usr/include when installed) wasn't taken because of GCC's
own copies in /usr/libdata/gcc{44,47}, which comes first
in the compiler's internal include search path.

Since it is a standard header, we want our version to be
taken, so stop installing GCC's version and remove it via
'make upgrade'.

There are no other standard headers in /usr/libdata/gcc{44,47}.
gcc44: Bring back an accidentally removed file.
<sys/cdefs.h>: Bring in a compatibility macro for C11's _Static_assert.

Apparently gcc47 has support outside of C11, but for processing our
<complex.h> with gcc44, this is necessary.

Taken-from: FreeBSD
Merge branch 'master' into gsocdrm_jfree