Copy Host header before modifying in get_domain()

[mocmocamoc]

At the moment get_domain() will strip the port number from the original Host header, meaning that subsequent functions that use the header will find it missing the port number. For example, redirect() calls get_domain() before itself retrieving the Host header, so the port number will always be gone before redirect() can get it.

[ronisaacson]

This is a valid issue, but a better fix is:

domain = apr_pstrdup(r->pool, domain);