[PATCH] bind VTY to other interfaces than localhost

Hi, in some usecases, for people knowing what they are doing, it maybe an advantage to control osmocombb over the network. Since the VTY is already network capable, it just needs to bind to an alternative network interface than localhost. Here is a patch for layer23 (mobile), having an option "-u" (because -v is the port). Passing "-u 0.0.0.0" would bind to any interface. If you think it is useful, please commit it in the git. Cheers Tim