add missing part for adding webrtc support to module screenshare

bigbluebutton-client/build.xml

...on/modules/screenshare/managers/WebRTCDeskshareManager.as

...odules/screenshare/managers/WebRTCPublishWindowManager.as

...modules/screenshare/managers/WebRTCViewerWindowManager.as

...reenshare/view/components/WebRTCDesktopPublishWindow.mxml

.../screenshare/view/components/WebRTCDesktopViewWindow.mxml