Further port of ssrmatching to EConstr.
Further port of ssrmatching to EConstr.

ejgallego/coq,ejgallego/coq,ejgallego/coq,Zimmi48/coq,ejgallego/coq,SkySkimmer/coq,Zimmi48/coq,coq/coq,coq/coq,SkySkimmer/coq,coq/coq,coq/coq,Zimmi48/coq,SkySkimmer/coq,SkySkimmer/coq,Zimmi48/coq