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.

Modified Files:
--------------
    pgsql/contrib/intarray:
        _int.h (r1.7 -> r1.8)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/intarray/_int.h.diff?r1=1.7&r2=1.8)
        _intbig_gist.c (r1.7 -> r1.8)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/intarray/_intbig_gist.c.diff?r1=1.7&r2=1.8)
    pgsql/contrib/ltree:
        _ltree_gist.c (r1.15 -> r1.16)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/_ltree_gist.c.diff?r1=1.15&r2=1.16)
        ltree.h (r1.12 -> r1.13)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/ltree.h.diff?r1=1.12&r2=1.13)
    pgsql/contrib/pg_trgm:
        trgm.h (r1.2 -> r1.3)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_trgm/trgm.h.diff?r1=1.2&r2=1.3)
        trgm_gist.c (r1.4 -> r1.5)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_trgm/trgm_gist.c.diff?r1=1.4&r2=1.5)
    pgsql/contrib/tsearch2:
        gistidx.c (r1.11 -> r1.12)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/gistidx.c.diff?r1=1.11&r2=1.12)
        gistidx.h (r1.5 -> r1.6)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/gistidx.h.diff?r1=1.5&r2=1.6)