offset for time part in UUIDs was 1/1000 of what it
should be. In other words, offset was off.

Also handle the case where we count into the future
when several UUIDs are generated in one "tick", and
then the next call is late enough for us to unwind
some but not all of those borrowed ticks.

Lastly, handle the case where we keep borrowing and
borrowing until the tick-counter overflows by also
changing into a new "numberspace" by creating a new
random suffix.

mysql-test/r/func_misc.result:
  Show that time-part of UUIDs is correct now.
mysql-test/t/func_misc.test:
  Show that time-part of UUIDs is correct now
  by replicating the C-code's resultin SQL.
  Results also decode to expect date-data on
  command-line (external validation).
  
  No test for unwinding of borrowed ticks as
  this a) is a race and b) depends on what timer
  we get.
sql/item_strfunc.cc:
  correct offset for date/time-part of UUID.
  also make sure that when we counted into
  the future earlier (several UUIDs generated
  in same tick), we only give back as many
  "borrowed" ticks as we can without duplicating
  past timestamps. If our tick-counter overflows
  before we can give back, or if the system-clock
  is set back (by user or Daylight Saving Time),
  we create a new random suffix to avoid
  collisions and clear the tick-counter.