monitor: Improve mux'ed console experience (Jan Kiszka)

Up to now, you never really knew if you already switched the console
after pressing CTRL-A C or if you mistyped it again. This patch
clarifies the situation by providing a prompt in a new line and
injecting a linebreak when switching away again. For this purpose, the
two events CHR_EVENT_MUX_IN and CHR_EVENT_MUX_OUT are introduced and
distributed on focus switches.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6716 c046a42c-6fe2-441c-8c8c-71466251a162