This code is not directly related to the template parser, so it
can safely live in its own file.
The only significant change to the code is to the signature of
`html_branches` so that it can be called without requiring a file.
Since it's only used in html_grep, that has been updated to reflect
this change.
Fixes: #1774.
Raghav Jajodia
Sahil Dua
Gordon P. Hemsley
Steve Howell