Allow alter of visitor location

Motivation

We need to set the visitors location based on other information that the given from the ip_geoloc module. It would also be great to set a different popup and tooltip text.

But for the moment we have no possibility to alter these informations.

Proposed resolution

Let other module alter the ip_geoloc_get_visitor_location() function. That modules can implement hook_ip_geoloc_get_visitor_location_alter().