Revert deprecation of IpAddr, stabilizing for 1.7

After [considerable
pushback](https://github.com/rust-lang/rfcs/issues/1451), it's clear
that there is a community consensus around providing `IpAddr` in the
standard library, together with other APIs using it.

This commit reverts from deprecated status directly to stable. The
deprecation landed in 1.6, which has already been released, so the
stabilization is marked for 1.7 (currently in beta; will require a backport).

src/libstd/net/mod.rs

@@ -18,7 +18,6 @@ use io::{self, Error, ErrorKind};
 use sys_common::net as net_imp;
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[allow(deprecated)]
 pub use self::ip::{IpAddr, Ipv4Addr, Ipv6Addr, Ipv6MulticastScope};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::addr::{SocketAddr, SocketAddrV4, SocketAddrV6, ToSocketAddrs};