Commands do not have a refspecurl

[Jeff Johnson]

IntStd table (associate interface with standards) has these four fields:

  `ISsid`
  `ISrefspec`
  `ISurl`
  `ISrefspecurl`

Allowing for doc pages to be provided from both the guiding standard and the
reference standard.

CmdStd table (associate command with standards) has only three:

  `CSsid`
  `CSrefspec`
  `CSurl`

that is, no refspecurl. The absence means that the description is not complete
in LSB Navigator when a manpage looks something like this:

===
at
Name
at -- examine or delete jobs for later execution
Description

at is as specified in POSIX 1003.1-2001 (ISO/IEC 9945-2003) but with
differences as listed below.
===

the Navigator page has a link for the page of which the above is a snippet, but
not to the underlying description in POSIX.

Filed this as a database request since although it's really just a Navigator
issue, it needs support from the database to make things work.