Fix [Z.div] and add [Z.modulo] in ExtrHaskellZNum.v
Fix [Z.div] and add [Z.modulo] in ExtrHaskellZNum.v

The previous extraction of [Z.div] for Haskell did not properly handle
divide-by-zero.  Fix it by introducing an explicit [if] statement in the
generated Haskell code.

Also, introduce a similar extraction rule for [Z.modulo], with the same
check for modulo-by-zero.

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