pgsql: Tweak dynahash.c to not allocate so many entries at once when

Log Message:
-----------
Tweak dynahash.c to not allocate so many entries at once when dealing
with a table that has a small predicted size. Avoids wasting several
hundred K on the timezone hash table, which is likely to have only one
or a few entries, but the entries use up 10Kb apiece ...

Modified Files:
--------------
pgsql/src/backend/utils/hash:
dynahash.c (r1.62 -> r1.63)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/hash/dynahash.c.diff?r1=1.62&r2=1.63)
pgsql/src/include/utils:
hsearch.h (r1.38 -> r1.39)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/hsearch.h.diff?r1=1.38&r2=1.39)
pgsql/src/timezone:
pgtz.c (r1.35 -> r1.36)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/timezone/pgtz.c.diff?r1=1.35&r2=1.36)