#129 Wrap diff output in a template

[Matt Brown]

Diff output (generated in the showDiff function in
lib/diff.php) is currently output directly to the
browser without being wrapped in a template.

As this function is called directly from main.php in
the same was as page edit or browse features, it also
needs to be wrapped in a template for consistency of
style.

The following patch wraps diff output in a template.

This patch is part of the WLUG Wiki merge to match the
current PHPwiki source and can be found in the WLUG SVN
repository as revision 29
http://svn.wlug.org.nz/viewcvs?root=wiki&view=rev&rev=29

[Matt Brown]

Add template wrapper for output of showDiff function