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)