[numtok] [zarith] Simplifications
[numtok] [zarith] Simplifications

Suggested by Pierre Roux

gares/coq,gares/coq,SkySkimmer/coq,coq/coq,ejgallego/coq,ejgallego/coq,gares/coq,coq/coq,Zimmi48/coq,gares/coq,JasonGross/coq,JasonGross/coq,Zimmi48/coq,SkySkimmer/coq,silene/coq,silene/coq,SkySkimmer/coq,gares/coq,ejgallego/coq,JasonGross/coq,JasonGross/coq,coq/coq,SkySkimmer/coq,Zimmi48/coq,coq/coq,silene/coq,ejgallego/coq,Zimmi48/coq