pgsql: Fix planner to do the right thing when a degenerate outer join

Log Message:
-----------
Fix planner to do the right thing when a degenerate outer join (one whose
joinclause doesn't use any outer-side vars) requires a "bushy" plan to be
created. The normal heuristic to avoid joins with no joinclause has to be
overridden in that case. Problem is new in 8.2; before that we forced the
outer join order anyway. Per example from Teodor.

Modified Files:
--------------
pgsql/src/backend/optimizer/geqo:
geqo_eval.c (r1.81 -> r1.82)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/geqo/geqo_eval.c.diff?r1=1.81&r2=1.82)
pgsql/src/backend/optimizer/path:
joinrels.c (r1.81 -> r1.82)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/joinrels.c.diff?r1=1.81&r2=1.82)
pgsql/src/backend/optimizer/util:
joininfo.c (r1.44 -> r1.45)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/joininfo.c.diff?r1=1.44&r2=1.45)
pgsql/src/include/optimizer:
joininfo.h (r1.31 -> r1.32)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/optimizer/joininfo.h.diff?r1=1.31&r2=1.32)