* new split algorithm (as proposed in http://archives.postgresql.org/pgsql-hackers/2006-06/msg00254.php)
* possible call pickSplit() for second and below columns
* add spl_(l|r)datum_exists to GIST_SPLITVEC -
pickSplit should check its values to use already defined
spl_(l|r)datum for splitting. pickSplit should set
spl_(l|r)datum_exists to 'false' (if they was 'true') to
signal to caller about using spl_(l|r)datum.
* support for old pickSplit(): not very optimal
but correct split
* remove 'bytes' field from GISTENTRY: in any case size of
value is defined by it's type.
* split GIST_SPLITVEC to two structures: one for using in picksplit
and second - for internal use.
* some code refactoring
* support of subsplit to rtree opclasses
TODO: add support of subsplit to contrib modules
boxes. Change interface to user-defined GiST support methods union and
picksplit. Now instead of bytea struct it used special GistEntryVector
structure.
with OPAQUE, as per recent pghackers discussion. I still want to do some
more work on the 'cstring' pseudo-type, but I'm going to commit the bulk
of the changes now before the tree starts shifting under me ...
