pgsql: Fix thinko in recent changes to handle ScalarArrayOpExpr as an

Log Message:
-----------
Fix thinko in recent changes to handle ScalarArrayOpExpr as an indexable
condition: when there are multiple possible index paths involving
ScalarArrayOpExprs, they are logically to be ANDed together not ORed.
This thinko was a direct consequence of trying to put the processing
inside generate_bitmap_or_paths(), which I now see was a bit too cute.
So pull it out and make the callers do it separately (there are only two
that need it anyway). Partially responds to bug #2441 from Arjen van der Meijden.
There are some additional infelicities exposed by his example, but they
are also in 8.1.x, while this mistake is not.

Modified Files:
--------------
pgsql/src/backend/optimizer/path:
indxpath.c (r1.204 -> r1.205)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/indxpath.c.diff?r1=1.204&r2=1.205)