Use of only "internal:" to link to front page does not get converted back to base url of site on render

When linking to the font page with

 <a href="/">Front Page</a>

or

  <a href="http://example.com/">Front Page</a>

the path is not caught by the render pass of pathfilter and a link to "internal:" is displayed.

Attached patch modifies the regular expression that looks for cases of "internal:" to replace with a call to url().

Cause was the requirement that a path be included after 'internal:'

Came to light after auto internalizer converted <a href="http://example.com">Front Page</a> into <a href="internal:">Front Page</a>

I apologize for the patch not being rooted at the module root. Mercurial won't make diffs how I would like. Can be applied with
patch -p6 < pathfilter-replacement-patterns-fix.patch