create role manual

While my colleague is working on translating
doc/src/sgml/ref/create_role.sgml into Japanese, he has found
following sentence is hard to parse:

   The rules for which initial
   role membership options are enabled described below in the
   <literal>IN ROLE</literal>, <literal>ROLE</literal>, and
   <literal>ADMIN</literal> clauses.

Maybe we need "are" in front of "described"?

Attached is the patch for that.

Best reagards,
--
Tatsuo Ishii
SRA OSS LLC
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp