First pass at integrating BIT and BIT VARYING code from Adriaan Joubert.

First pass at integrating BIT and BIT VARYING code from Adriaan Joubert.
Update functions to new-style fmgr, make BIT and VARBIT be binary-
equivalent, add entries to allow these types to be btree indexed,
correct a few bugs.  BIT/VARBIT are now toastable, too.
NOTE: initdb forced due to catalog updates.