new createuser option for replication role

Hi,

Currently createuser cannot create a role with REPLICATION privilege
because it doesn't have any option to do that. Which sometimes annoys
me when setting up replication. I'd like to propose to add new options
"-x (--replication)" and "-X (--no-replication)" into createuser. "-x" allows
the new user to do replication, and "-X" disallows. The default is "-X".
Is it worth creating the patch?

Though I'd like to use "-r" and "-R" as the option name, they have already
been used for CREATEROLE privilege. So I'm thinking to use "-x" and
"-X" derived from XLOG. But does anyone have better option name?

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center