pgsql: Fix check for whether a clauseless join has to be forced in the

Log Message:
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Fix check for whether a clauseless join has to be forced in the presence of
outer joins. Originally it was only looking for overlap of the righthand
side of a left join, but we have to do it on the lefthand side too.
Per example from Jean-Pierre Pelletier.

Modified Files:
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pgsql/src/backend/optimizer/geqo:
geqo_eval.c (r1.80 -> r1.81)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/geqo/geqo_eval.c.diff?r1=1.80&r2=1.81)
pgsql/src/backend/optimizer/path:
joinrels.c (r1.80 -> r1.81)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/joinrels.c.diff?r1=1.80&r2=1.81)