Updated libxml2-fix Plugin for WordPress

I made a small update to the libxml2-fix WordPress plugin this morning. There are few more odd combinations of PHP + libxml2 that have problems, so this change applies the work around as long as the libxml2 version is below 2.7.3. That saves on having to list all of the individual versions that may have this issue. This improvement was submitted by Danilo Ercoli.

I’m bummed that there are still so many hosts running known to be broken combinations of PHP + libxml2. In the meantime we may as well make it easier for people to work around the issue.