pgsql: It seems the YYLLOC_DEFAULT macro recommended by the Bison 1.875

Log Message:
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It seems the YYLLOC_DEFAULT macro recommended by the Bison 1.875 manual
just doesn't work with Bison 2.0 ... fix it ...

Modified Files:
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pgsql/src/backend/parser:
gram.y (r2.535 -> r2.536)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y.diff?r1=2.535&r2=2.536)