xfer: Use hook_connect() for receiving chats

fixes #160
xfer: bind to wildcard address when sending

When #5 was fixed, we started to always bind to the local address
connected to the irc server because the xfer.network.own_ip address
may not be able to be bound to when NATed. But this means when the
own_ip address is a different family (IPv4 vs IPv6) from the irc
server connection, we were listening for connections on the wrong
interface.

This patch lets us figure out which family is being used,
(xfer.network.own_ip's family, or the irc connection's family
otherwise) and bind() into the correct family via that family's
wildcard address.
doc: add list of bar items not used in bars by default (user's guide)
core: add Travis CI builds with Python 3 and without GnuTLS
doc: update German documentation
core: add option weechat.completion.command_inline (task #12491)
core: update German translations
doc: update German auto-generated files
Merge branch 'xfer_wildcard' of git://github.com/talisein/weechat-1 into talisein-xfer_wildcard
xfer: return 0/1 instead of WEECHAT_RC_OK/ERROR in function xfer_resolve_addr
core: update translations
xfer: fix comments
core: update ChangeLog
Merge branch 'xfer_chat' of git://github.com/talisein/weechat-1 into talisein-xfer_chat
xfer: fix code style
core: update translations
core: update ChangeLog
core: update Japanese translations
Merge pull request #252 from l/translation_ja

core: update Japanese translations
doc: update Japanese auto-generated files