correct Pause key sequence

If you press the keys Windows+Pause, it does not bring up the System Info panel as it should.  This is because the Pause key should send a single fastpath input PDU with four key events, including two of them with an undocumented E1-control-code bit set.   This patch adds the code to send that four-key PDU when pause is pressed, including the undocumented bit.  (The current code sends four separate PDUs and does not know about the undocumented E1 bit.)

Note:  I did not test the non-fastpath code since I have no servers set up for it; and I did not add this pause-fix to non-Linux clients, since I am not set up to build and test for those clients.  This should be ported to master branch as well.