Fix warnings about non-string-literals on printf()-like functions.

qWarning() and similar functions expect a format string as first
parameter.

Using QString's formatting, you should not pass it as first parameter,
but use the "%s" format instead. It's very difficult but it might lead
to format string vulnerabilities.

Signed-off-by: Manuel Nickschas <sputnick@quassel-irc.org>