MMapPositive: some improvements
MMapPositive: some improvements

 Most of them are backports of improvements already there in
 FSetPositive when compared with the original FMapPositive file.

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