Bugfix release (at least) for Xfce

• Fix a long standing bug with a flood of error 143 (BadPicture) request 139 minor 8 serial 2769 errors if xfdesktop is running 1739439
• Fix frozen pixmap if windows are moved and resized (almost) at the same time 92ec779

Fix double-shadow in chrome-based windows

• Do not draw shadows on _GTK_FRAME_EXTENTS windows ac38db0
• Fail early, if another compositing manager is already running ac38db0

Minor Bugfix Release

• Fix error message flood on xfce 4.18 6df8a24
• Don't draw shadows on zoom's screenshare widgets, amongst others 1b158ec
• Be compatible with some screenshooter apps (ignore override_redirect windows) 73f40f9

First public release.

Having bugfixed and tuned an early version of compton, this is the first public release.