Fix #3994: Switching on realtime rendering might cause irresponsiveness of Camera
Refinement for #3994: fix crashes at shutdown in Windows

Don't call Yield() in CamWnd::onFrame since it might actually process a
pending application shutdown event,. This case leads to problems when
trying to stop the CamWnd timer. A timer message might still be left in
the Win32 message queue which in turn leads to crashes in
CamWnd::onFrame.
Merge changes from master.
Refactor methods a bit to avoid redundancy.
Fix chase mouse behaviour.

This is now applicable for mouse tools with capture pointer mode only.