net.connect: Default to *a pattern if none provided

net.http: Rename handler to conn, for consistency with all our other code

net.http: Remove use of 'conn' (raw socket object returned by addclient)

moduleapi: Remove unused and undocumented :has_feature and :has_identity

doc: Add template / API specification for net.server (thanks Daurnimator)

net.connect: New API for outgoing connections, based on 'service resolvers'

net.server_event: Not every instantly-readable connection is an error, continue if possible

net.server_event: Better outgoing connection error handling Same as 67311cda0625. Check for readability. If a socket is readable after initial connection, it likely means an error, so we call the readcallback for that connection to handle it (and ultimately close).

net.server_select: Better detection of errors for outgoing connections On connection failure, a socket is marked readable and writable. So to detect initial connection failures (connection refused, etc.) we now watch for sockets becoming readable during initial connection, and also read from readable sockets before writing to writable sockets. This should fix 'onconnect' being called for outgoing connections that actually failed.

MUC: Emit 333 status code on presence as per XEP-0045 1.30 (fixes #1087)