Log Message:-----------Add "May/Can/Might" section to error message style guidlines, and"can't" -> "cannot" section.
Modified Files:-------------- pgsql/doc/src/sgml: sources.sgml (r2.25 -> r2.26) (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/sources.sgml.diff?r1=2.25&r2=2.26)
