Currently, qInstallMsgHandler() does not return the
handle to the default message handler. This patch defines
a default message handler. This is returned by
qInstallMsgHandler() when called for the first time. A call
to qInstallMsgHandler(0) will restore the default message
handler as was the case previously.
Change-Id: I42f06654d45fb0e633f3c6d912fc8f05c23249aa
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
124044613d