bugfixes and restoring backwards compatibility of Combinatorial DT reco

This is an update of the "physics changes" that were taken out of #3450. 
The performance of HLT muons should return to the state from pre4, as HLT muons use the (old) combinatorial pattern recognition DT algorithm.
The same should happen to cosmic muons as they also use the old algorithm, though this is changing right now (#3722).

Reco muons change little from pre5/pre6 and the changes should in general be improvements (slightly better segments chi2, better segment angular resolution etc)