gcc's athlon64 mtune cpu type doesn't match it's config.guess cpu type, so accommodate.  silly hack should be made into proper configure compiler option tests, but that's a bigger effort.
gcc's athlon64 mtune cpu type doesn't match it's config.guess cpu type, so accommodate.  silly hack should be made into proper configure compiler option tests, but that's a bigger effort.

git-svn-id: 67bf12f30ddf2081c31403e0b02b2123541f1680@11736 08b3d480-bf2c-0410-a26f-811ee3361c24

kongr45gpen/bzflag,khonkhortisan/bzflag,kongr45gpen/bzflag,kongr45gpen/bzflag,khonkhortisan/bzflag,kongr45gpen/bzflag,khonkhortisan/bzflag,kongr45gpen/bzflag,adamsdadakaeti/bzflag,khonkhortisan/bzflag,adamsdadakaeti/bzflag,adamsdadakaeti/bzflag,kongr45gpen/bzflag,kongr45gpen/bzflag,adamsdadakaeti/bzflag,kongr45gpen/bzflag,adamsdadakaeti/bzflag,khonkhortisan/bzflag,adamsdadakaeti/bzflag,adamsdadakaeti/bzflag,khonkhortisan/bzflag,khonkhortisan/bzflag