Add a space in cast since cast binds loosely.
Add a space in cast since cast binds loosely.

Fixes bug 3936
This closes #73

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