Only disable -Wtype-limits on GCC 4.3 and newer (earlier versions don't have this option).
Only disable -Wtype-limits on GCC 4.3 and newer (earlier versions don't have this option).

Also, make sure we're on GCC before attempting to set either of these options.

refs #249

isis-ammo/ammo-gateway,isis-ammo/ammo-gateway,isis-ammo/ammo-gateway,isis-ammo/ammo-gateway,isis-ammo/ammo-gateway,isis-ammo/ammo-gateway