pgsql: Add regression test for macaddr type.

Log Message:
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Add regression test for macaddr type. Enhance documentation about accepted
input formats.

Modified Files:
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pgsql/doc/src/sgml:
datatype.sgml (r1.228 -> r1.229)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datatype.sgml?r1=1.228&r2=1.229)
pgsql/src/test/regress:
parallel_schedule (r1.47 -> r1.48)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/parallel_schedule?r1=1.47&r2=1.48)
serial_schedule (r1.44 -> r1.45)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/serial_schedule?r1=1.44&r2=1.45)

Added Files:
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pgsql/src/test/regress/expected:
macaddr.out (r1.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/macaddr.out?rev=1.1&content-type=text/x-cvsweb-markup)
pgsql/src/test/regress/sql:
macaddr.sql (r1.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/macaddr.sql?rev=1.1&content-type=text/x-cvsweb-markup)