Revert last three commits which have been unintentially pushed to master
Revert "updated casa-source to most recent casa6 CAS-13857 changes"
Revert "Fix code for casacore changes"
Revert "Set casa6 branch commit and add X11 dir"
This reverts commit debc2a9b01bd0455b85bb484cddb019dd93c69e4.
This reverts commit 88a5009f7ac1d12c0aa466bffc432666b1626653.
This reverts commit 88a5009f7ac1d12c0aa466bffc432666b1626653.