#130 Always prefer legible author name over author_id property

[Matt Brown]

Currently the getAuthorMessage function prefers the
author_id property of the revision and only uses the
author property if the author_id is empty.

This is a less than optimal situation as the author_id
is usually an illegible string such as an IP address.
It is much preferable to use the reverse situation:

Prefer the author (which is a legible string eg.
MattBrown) and fall back to the author_id only if the
author property is not available.

This patch implements that preferred behaviour.

This patch is part of the WLUG Wiki merge to be
consistent with upstream PHPwiki. It relates to
revision 33 of the WLUG SVN repository.
http://svn.wlug.org.nz/viewcvs?root=wiki&view=rev&rev=33

[Matt Brown]

Always prefer author property over author_id