settings: Add option to disable lowering windows on middle click

This has no effect on CSD windows.

Closes #280

Signed-off-by: Andre Miranda <andreldm@xfce.org>
2 jobs for !25 with issue-280 in 2 minutes and 52 seconds (queued for 3 seconds)
latest detached
Status Job ID Name Coverage
  Build
passed #11920
build

00:01:09

 
  Distcheck
passed #11921
distcheck

00:01:43