[zarith] [notation] Build less intermediate values
[zarith] [notation] Build less intermediate values

We could still optimize the functions in that file a bit more if there
is need.

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