Logging: Change arguments of message handler to avoid conversions

Logging: Change arguments of message handler to avoid conversions

Introduce a new QtMessageHandler that takes QString instead of
char *: This avoids converting to local8bit , only to convert it back
to utf16 for Windows.

The old QMessageHandler is kept for a transition period, but will
be removed before Qt 5.0.

Also fix qEmergencyOut (that is called in OOM situations) to not rely
on the default message handler.

Change-Id: Iee0ce5838f97175c98788b847964273dd22d4a37
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>