Typeclasses: allow shelved subgoals
Typeclasses: allow shelved subgoals

Be more lenient, allowing non-class subgoals to remain
after resolution, this seems necessary when launching
resolution in goals containing evars.

Also put a tclONCE when hints don't need to backtrack.

coq/coq,amintimany/coq,ppedrot/coq,william-lawvere/coq,Zimmi48/coq,gares/coq,silene/coq,JasonGross/coq,maximedenes/coq,ppedrot/coq,william-lawvere/coq,Lionel-Rieg/coq,Ptival/coq,SkySkimmer/coq,mattam82/coq,gares/coq,ejgallego/coq,maximedenes/coq,maximedenes/coq,gares/coq,ppedrot/coq,ejgallego/coq,ejgallego/coq,gares/coq,Matafou/coq,maximedenes/coq,Zimmi48/coq,Ptival/coq,JasonGross/coq,maximedenes/coq,silene/coq,coq/coq,Lionel-Rieg/coq,coq/coq,mattam82/coq,letouzey/coq-wip,amintimany/coq,letouzey/coq-wip,SkySkimmer/coq,gares/coq,Matafou/coq,coq/coq,JasonGross/coq,Matafou/coq,Lionel-Rieg/coq,Ptival/coq,ppedrot/coq,mattam82/coq,JasonGross/coq,letouzey/coq-wip,SkySkimmer/coq,Zimmi48/coq,letouzey/coq-wip,ejgallego/coq,silene/coq,william-lawvere/coq,letouzey/coq-wip,SkySkimmer/coq,ppedrot/coq,Zimmi48/coq,amintimany/coq