This setting allows you to control the maximum number of lines before disabling syntax highlighting.  Pygments can be extremely slow on large files.  The default (no limit) doesn't change any behavior.  I set this to 10000 on my site to handle some large files.

I thought I had posted this patch before, but I couldn't find it.  I just went through updating this to work with the new admin siteconfig stuff.

- Initially set up with no setting, syntax highlighting had no limit.
- Set limit to 10000, files larger than that had syntax highlighting disabled.