Can no longer get `SocketType` from active socket

[gregorycollins]

Hi,

You used to be able to get the SocketType from an active Socket by pattern-matching the MkSocket constructor. Since 3.0 this no longer seems to be possible. This breaks io-streams-haproxy. We should expose a getSocketType :: Socket -> SocketType. I'll prepare a PR

[kazu-yamamoto]

Sorry for your incovenience.
Would you add "Since: " to its document?