189050f3f4
Filter out control characters (U+0000 to U+001F) from outgoing messages, as they are illegal in XML 1.0 (except for \t, \n, and \r). This prevents XMPP servers from closing the connection when such characters are accidentally or intentionally included in a message. Fixes: https://github.com/profanity-im/profanity/issues/1437