Thread: pgsql: Document aliases for our supported encodings.

Log Message:
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Document aliases for our supported encodings.

Add a few encodings that were not documented.

Modified Files:
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    pgsql/doc/src/sgml:
        charset.sgml (r2.50 -> r2.51)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/charset.sgml.diff?r1=2.50&r2=2.51)
    pgsql/src/backend/utils/mb:
        encnames.c (r1.23 -> r1.24)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/mb/encnames.c.diff?r1=1.23&r2=1.24)