gx: update go-multihash

[Stebalien]

Depends on:

• https://github.com/libp2p/go-libp2p-peer/pull/20
• https://github.com/libp2p/go-libp2p-secio/pull/23
• https://github.com/multiformats/go-multiaddr/pull/61
• https://github.com/multiformats/go-multiaddr-net/pull/33
• https://github.com/whyrusleeping/iptb/pull/37
• https://github.com/whyrusleeping/mafmt/pull/7
• https://github.com/libp2p/go-libp2p-peerstore/pull/18
• https://github.com/ipfs/go-ipfs-util/pull/6
• https://github.com/libp2p/go-libp2p-transport/pull/25
• https://github.com/libp2p/go-peerstream/pull/19
• https://github.com/libp2p/go-libp2p-loggables/pull/14
• https://github.com/libp2p/go-tcp-transport/pull/17
• https://github.com/libp2p/go-maddr-filter/pull/4
• https://github.com/libp2p/go-ws-transport/pull/28
• https://github.com/libp2p/go-addr-util/pull/9
• https://github.com/ipfs/go-cid/pull/39
• https://github.com/libp2p/go-testutil/pull/15
• https://github.com/libp2p/go-libp2p-interface-conn/pull/4
• https://github.com/libp2p/go-libp2p-interface-pnet/pull/6
• https://github.com/libp2p/go-libp2p-conn/pull/21
• https://github.com/libp2p/go-libp2p-net/pull/15
• https://github.com/libp2p/go-libp2p-metrics/pull/7
• https://github.com/libp2p/go-libp2p-interface-connmgr/pull/2
• https://github.com/libp2p/go-libp2p-host/pull/10
• https://github.com/libp2p/go-libp2p-swarm/pull/46
• https://github.com/libp2p/go-libp2p-nat/pull/4
• https://github.com/libp2p/go-libp2p-netutil/pull/16
• https://github.com/libp2p/go-libp2p-blankhost/pull/7
• https://github.com/libp2p/go-libp2p-circuit/pull/24
• https://github.com/multiformats/go-multiaddr-dns/pull/6
• https://github.com/libp2p/go-libp2p/pull/251
• https://github.com/libp2p/go-libp2p-record/pull/7
• https://github.com/libp2p/go-libp2p-kbucket/pull/16
• https://github.com/libp2p/go-libp2p-routing/pull/19
• https://github.com/libp2p/go-libp2p-kad-dht/pull/105
• https://github.com/jbenet/hang-fds/pull/2
• https://github.com/libp2p/go-floodsub/pull/51
• https://github.com/ipfs/go-block-format/pull/9
• https://github.com/ipfs/go-ipld-format/pull/30
• https://github.com/ipfs/go-ipld-cbor/pull/31
• https://github.com/libp2p/go-libp2p-dummy-conn/pull/5
• https://github.com/libp2p/go-libp2p-pnet/pull/17
• https://github.com/ipfs/go-ipfs-cmdkit/pull/7
• https://github.com/ipfs/go-ipfs-cmds/pull/33

This PR with gx updates has been created using gx-workspace: https://github.com/ipfs/gx-workspace