Revert "MUC: ignore non-error, non-echos from the MUC"
Revert "MUC: ignore non-error, non-echos from the MUC"

This reverts commit d4d5a2f99eb5e1a2471662c09ff04aee865dde36.

This enables receiving messages from channel (information about changed subject)

Examples:

<message from='devel@conference.pidgin.im' to='erlehmann@jabber.ccc.de/Gajim' type='groupchat'>
<body>Dieser Raum ist nicht anonym</body>
<x xmlns='http://jabber.org/protocol/muc#user'>
<status code='100'/>
</x>
</message>

<message from='devel@conference.pidgin.im' to='erlehmann@jabber.ccc.de/Gajim' type='groupchat'>
<subject>Pidgin, Finch, and libpurple development headquarters</subject>
<body>rekkanoryo hat das Thema geändert auf: Pidgin, Finch, and libpurple development headquarters</body>
</message>
<r xmlns='urn:xmpp:sm:2'/>

community-ssu/telepathy-gabble,community-ssu/telepathy-gabble,community-ssu/telepathy-gabble,community-ssu/telepathy-gabble