mostly revert r638 - failed completely

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robustbase@639 694ef91d-65df-0310-b7bb-92e67a308ead
much less stringent, notably for "a4" (= milk data) - try to adapt to 32bit

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robustbase@640 694ef91d-65df-0310-b7bb-92e67a308ead
small covMcd() tweaks

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robustbase@641 694ef91d-65df-0310-b7bb-92e67a308ead