feature freeze and beta schedule

The schedule
<https://wiki.postgresql.org/wiki/PgCon_2014_Developer_Meeting#9.5_Schedule>
calls for beta in June.  In light of that, the core team has agreed to
call for
   feature freeze on May 15

That means that all patches that add or change features should be
committed by then.

If you have spare cycles, there are a number of relevant patches still
open in the commit fest.