interface.rng: fix regexp for ipv4-addr and simplify ipv4-prefix
interface.rng: fix regexp for ipv4-addr and simplify ipv4-prefix

The regexp for ipv4-addr was too permissive. The restriction on ipv4-prefix
is simpler if we take it to be a number.

Removed comment that didn't make any sense anymore

osier/netcf,hallyn/netcf,hallyn/netcf,seanbruno/fbsd-netcf,seanbruno/fbsd-netcf,seanbruno/fbsd-netcf,emaste/netcf,battlemidget/deprecated-mingw32-netcf,battlemidget/deprecated-mingw32-netcf,emaste/netcf,osier/netcf,hallyn/netcf,osier/netcf,emaste/netcf