crm_update_location() deletes absent passed parameter values

The crm_update_location() API call deletes absent parameters for locations, requiring you to pass all email, phone, IM objects as well as any other relevant / required attributes. This is contrary to the documentation, which infers that only the parameters you pass will be updated, and the rest will be left as-is. Here is a patch I have dveloped for 5.1 against api/Location.php.