pgsql: Replace bitwise looping with bytewise looping in hemdistsign and

Log Message:
-----------
Replace bitwise looping with bytewise looping in hemdistsign and
sizebitvec of tsearch2, as well as identical code in several other
contrib modules.  This provided about a 20X speedup in building a
large tsearch2 index ... didn't try to measure its effects for other
operations.  Thanks to Stephan Vollmer for providing a test case.

Tags:
----
REL8_1_STABLE

Modified Files:
--------------
    pgsql/contrib/intarray:
        _int.h (r1.4 -> r1.4.6.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/intarray/_int.h.diff?r1=1.4&r2=1.4.6.1)
        _intbig_gist.c (r1.6 -> r1.6.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/intarray/_intbig_gist.c.diff?r1=1.6&r2=1.6.2.1)
    pgsql/contrib/ltree:
        _ltree_gist.c (r1.11.2.1 -> r1.11.2.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/_ltree_gist.c.diff?r1=1.11.2.1&r2=1.11.2.2)
        ltree.h (r1.12 -> r1.12.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/ltree.h.diff?r1=1.12&r2=1.12.2.1)
    pgsql/contrib/pg_trgm:
        trgm.h (r1.2 -> r1.2.6.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_trgm/trgm.h.diff?r1=1.2&r2=1.2.6.1)
        trgm_gist.c (r1.3 -> r1.3.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_trgm/trgm_gist.c.diff?r1=1.3&r2=1.3.2.1)
    pgsql/contrib/tsearch2:
        gistidx.c (r1.10 -> r1.10.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/gistidx.c.diff?r1=1.10&r2=1.10.2.1)
        gistidx.h (r1.4 -> r1.4.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/gistidx.h.diff?r1=1.4&r2=1.4.2.1)