Change end of line format detection logic to match vims
Change end of line format detection logic to match vims

Only consider a buffer to be Crlf if *all* of its lines use it, else
consider it as Lf with embedded Cr chars.

Fixes #686

ekie/kakoune,ekie/kakoune,lenormf/kakoune,flavius/kakoune,occivink/kakoune,jjthrash/kakoune,mawww/kakoune,lenormf/kakoune,danr/kakoune,Somasis/kakoune,danr/kakoune,ekie/kakoune,casimir/kakoune,mawww/kakoune,jjthrash/kakoune,casimir/kakoune,jjthrash/kakoune,jkonecny12/kakoune,alexherbo2/kakoune,flavius/kakoune,casimir/kakoune,lenormf/kakoune,Somasis/kakoune,jkonecny12/kakoune,mawww/kakoune,flavius/kakoune,flavius/kakoune,occivink/kakoune,occivink/kakoune,jkonecny12/kakoune,alexherbo2/kakoune,alexherbo2/kakoune,mawww/kakoune,jkonecny12/kakoune,Somasis/kakoune,danr/kakoune,Somasis/kakoune,alexherbo2/kakoune,jjthrash/kakoune,ekie/kakoune,danr/kakoune,lenormf/kakoune,occivink/kakoune,casimir/kakoune