document about pg_ctl kill

Hi,

pg_ctl kill requires signal name and process ID, but they are enclosed in
brackets in the document as follows.

    pg_ctl kill [signal_name] [process_id]
    http://developer.postgresql.org/pgdocs/postgres/app-pg-ctl.html

Should we remove those brackets? The attached patch does that.

Regards,

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