libstd: Implement {peer, socket}_name for new rt tcp & udp.
libstd: Fix errors when rtdebug! is not a noop.
libstd: Handle IPv4-Mapped/Compatible IPv6 addresses.
libstd: Get rid of duplication in {peer, socket}_name and remove extra *.
libstd: Add ToStr impl for IpAddr.
libstd: Implement some missing tcp methods.
libstd: Implement some missing udp methods.
libstd: Tests for {peer, socket}_name.
auto merge of #8040 : luqmana/rust/rtn, r=brson

Implements various missing tcp & udp methods.. Also fixes handling ipv4-mapped/compatible ipv6 addresses and addresses the XXX on `status_to_maybe_uv_error`.

r? @brson