fix bug with inconsistent selection of default mask length for
"class D" addresses.  Per report from Steve Atkins.

information.

right in the failure.  We can always re-add it if required.

but the documentation still said so.

Kris Jurka

with Postgres.

clamp the estimated number of groups to table row count over 10, instead
of table row count; this reflects a heuristic that people probably won't
group over a near-unique set of columns, and the knowledge that we don't
currently have any way to estimate the correlation of the columns better
than guessing.  This change creates a trivial plan change in one of the
regression tests.

look at the actual aggregate transition datatypes and the actual overhead
needed by nodeAgg.c, instead of using pessimistic round numbers.
Per a discussion with Michael Tiemann.

defining List.

Solaris and should be a little faster anyway, since in most scenarios
all but perhaps the last path component will already exist.

functions of the aggregate, at both aggregate creation and execution times.

utils/cache/lsyscache.c where it can be used by other things.  Also
cleans up both get_usesysid() and get_grosysid() a bit. From Stephen
Frost.