support for .php3 files

Some of our customers use .php3 files, because some CMS (eg. SPIP) has used in the past that file extension, and we need to maintain support for .php3 files for compatibility.

I have added php3 files support adding in VirtualHost these directives

(...)
AddHandler fcgid-script .php3
(...)
FCGIWrapper /home/xxxx/xxxxx/fcgi-bin/php5.fcgi .php3
(...)
RemoveHandler .php3
(...)

But if the customer change PHP version by "Server Configuration - PHP Versions", Virtualmin overwrite the custom configuration and support for php3 files disapear.

The server setup is

Debian 4.0
Virtualmin Pro
webmin-virtual-server 3.56

Debian oficial packages:
apache2-mpm-worker 2.2.3-50vm
php4-cgi 4.4.4-8+etch4
php5-cgi 5.2.0-8+etch10