pgsql: Break out \distv into four separate lines in the psql

Log Message:
-----------
Break out \distv into four separate lines in the psql documentation, for
clarity.

Modified Files:
--------------
pgsql/doc/src/sgml/ref:
psql-ref.sgml (r1.215 -> r1.216)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/psql-ref.sgml?r1=1.215&r2=1.216)