Fixing part of HoTT bug #61 (in declare_evar_from_virtual_equation, fix the type of the term which has to be in the signature of the evar to declare); some problems remain though (see next commit).
Fixing part of HoTT bug #61 (in declare_evar_from_virtual_equation,
fix the type of the term which has to be in the signature of the evar
to declare); some problems remain though (see next commit).

asr/coq,SkySkimmer/coq,gares/coq,JasonGross/coq,gares/coq,TheTypoMaster/coq,JasonGross/coq,silene/coq,coq/coq,TheTypoMaster/coq,Ptival/coq,SkySkimmer/coq,SkySkimmer/coq,shindere/coq,Matafou/coq,Lionel-Rieg/coq,TheTypoMaster/coq,herbelin/github-coq,ejgallego/coq,gares/coq,pirapira/coq2rust,maximedenes/coq,Matafou/coq,TOSPIO/coq,JasonGross/coq,jpdeplaix/coq,ppedrot/coq,mlasson/coq,TOSPIO/coq,ale-f/coq,barras/coq,Lionel-Rieg/coq,ale-f/coq,Ptival/coq,jpdeplaix/coq,mlasson/coq,aspiwack/coq,Ptival/coq,Zimmi48/coq,amintimany/coq,aspiwack/coq,barras/coq,ppedrot/coq,mattam82/coq,coq/coq,letouzey/coq-wip,william-lawvere/coq,JasonGross/coq,barras/coq,pirapira/coq2rust,amintimany/coq,shindere/coq,maximedenes/coq,gares/coq,letouzey/coq-wip,gmalecha/coq,maximedenes/coq,aspiwack/coq,Zimmi48/coq,gmalecha/coq,letouzey/coq-wip,TOSPIO/coq,amintimany/coq,SkySkimmer/coq,Lionel-Rieg/coq,mattam82/coq,herbelin/github-coq,Zimmi48/coq,maximedenes/coq,shindere/coq,ejgallego/coq,ale-f/coq,8l/coq,herbelin/github-coq,coq/coq,gmalecha/coq,asr/coq,mattam82/coq,Matafou/coq,mlasson/coq,ppedrot/coq,asr/coq,gares/coq,coq/coq,ppedrot/coq,pirapira/coq2rust,Zimmi48/coq,maximedenes/coq,ejgallego/coq,william-lawvere/coq,silene/coq,william-lawvere/coq,8l/coq,ejgallego/coq,letouzey/coq-wip,8l/coq,jpdeplaix/coq,ppedrot/coq,letouzey/coq-wip,silene/coq