ltsReg.default(): give a human-readable error msg early, when .fastlts()
		  has NA coefficients


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robustbase@582 694ef91d-65df-0310-b7bb-92e67a308ead
lmrob.tau() speed up:  
   using faster .Mpsi() instead of Mpsi() etc, notably
   useful in the many numerical integrations.


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robustbase@583 694ef91d-65df-0310-b7bb-92e67a308ead
update for release

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/robustbase@584 694ef91d-65df-0310-b7bb-92e67a308ead