pgsql: Add support to dynahash.c for partitioning shared hashtables

Log Message:
-----------
Add support to dynahash.c for partitioning shared hashtables according
to the low-order bits of the entry hash value. Also make some incidental
cleanups in the dynahash API, such as not exporting the hash header
structs to the world.

Modified Files:
--------------
pgsql/src/backend/storage/ipc:
shmem.c (r1.93 -> r1.94)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/ipc/shmem.c.diff?r1=1.93&r2=1.94)
pgsql/src/backend/storage/lmgr:
lock.c (r1.166 -> r1.167)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/lmgr/lock.c.diff?r1=1.166&r2=1.167)
pgsql/src/backend/utils/hash:
dynahash.c (r1.69 -> r1.70)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/hash/dynahash.c.diff?r1=1.69&r2=1.70)
pgsql/src/include/utils:
hsearch.h (r1.43 -> r1.44)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/hsearch.h.diff?r1=1.43&r2=1.44)