pgsql: Marginal hack to use a specialized hash function for dynahash

Log Message:
-----------
Marginal hack to use a specialized hash function for dynahash hashtables
whose keys are OIDs.  The only one that looks particularly performance
critical is the relcache hashtable, but as long as we've got the function
we may as well use it wherever it's applicable.

Modified Files:
--------------
    pgsql/src/backend/postmaster:
        pgstat.c (r1.91 -> r1.92)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/pgstat.c.diff?r1=1.91&r2=1.92)
    pgsql/src/backend/utils/cache:
        relcache.c (r1.220 -> r1.221)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/cache/relcache.c.diff?r1=1.220&r2=1.221)
        typcache.c (r1.12 -> r1.13)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/cache/typcache.c.diff?r1=1.12&r2=1.13)
    pgsql/src/backend/utils/fmgr:
        fmgr.c (r1.93 -> r1.94)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/fmgr/fmgr.c.diff?r1=1.93&r2=1.94)
    pgsql/src/backend/utils/hash:
        hashfn.c (r1.22 -> r1.23)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/hash/hashfn.c.diff?r1=1.22&r2=1.23)
    pgsql/src/include/utils:
        hsearch.h (r1.34 -> r1.35)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/hsearch.h.diff?r1=1.34&r2=1.35)