CrashHandler: Handle signal SIGABRT

This signal is generated if abort() is called. This happens e.g.
  1. if there is an attempt to call a pure virtual method
  2. if Qt detects an uncaught exception or printing a message fails
     (qlogging.cpp, qt_message())

Change-Id: I6a1d8f094a884ebc6bfc6a1fc168aea8afe825b5
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>