Use 127.0.0.1 for mapserver Allow statement

localhost may map to an IPv6 on some system, so disambiguate this by using 127.0.0.1 instead of localhost. I intially wanted to use "Allow from 127.0.0.1 ::1" but it does not work on Windows, as reported by @kalbermattenm in https://github.com/camptocamp/sitn_c2cgeoportal/pull/258#issuecomment-17800578.