Fix bug in native compiler with universe polymorphism.
Fix bug in native compiler with universe polymorphism.

Universe instances for constructors were not always correct, for instance in:
[cons _ list (nil _)] with a polymorphic [list] type, [nil] was receiving an
empty instance.

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