Explain Qt's behaviour with regards to exceptions in client code slots.
Explain Qt's behaviour with regards to exceptions in client code slots.

As mentioned in the comments of QTBUG-27548, we should make it clear
that unhandled exceptions in slots in Qt applications will result in
undefined behaviour.

Task-number: QTBUG-27548

Change-Id: I92734b05b5a05e00c58159e3830e901f8147b9da
Reviewed-by: Mitch Curtis <a74594a5101269175fe1b140badc4c0b6f699d25@digia.com>
Reviewed-by: Thiago Macieira <0ed1648d92ca0373297a182b1dba1b974ad10d88@intel.com>

kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc