stdlib: make cl based compilation reasonable
stdlib: make cl based compilation reasonable

`-Wall` with the clang-cl interface gives us `-Weverything` effectively,
which really reduces the effectiveness of the warnings.  Switch to `/W3`
which is roughly equivalent to `-Wall` in clang mode.

tkremenek/swift,lorentey/swift,rudkx/swift,jckarter/swift,nathawes/swift,JGiola/swift,stephentyrone/swift,jckarter/swift,hooman/swift,karwa/swift,shajrawi/swift,shajrawi/swift,jckarter/swift,ahoppen/swift,xedin/swift,nathawes/swift,harlanhaskins/swift,atrick/swift,roambotics/swift,gribozavr/swift,hooman/swift,CodaFi/swift,ahoppen/swift,sschiau/swift,shahmishal/swift,rudkx/swift,ahoppen/swift,rudkx/swift,parkera/swift,gribozavr/swift,glessard/swift,glessard/swift,apple/swift,lorentey/swift,practicalswift/swift,apple/swift,karwa/swift,practicalswift/swift,JGiola/swift,practicalswift/swift,jckarter/swift,JGiola/swift,aschwaighofer/swift,stephentyrone/swift,jmgc/swift,parkera/swift,airspeedswift/swift,stephentyrone/swift,benlangmuir/swift,JGiola/swift,sschiau/swift,allevato/swift,hooman/swift,xedin/swift,shahmishal/swift,gribozavr/swift,xwu/swift,glessard/swift,gribozavr/swift,parkera/swift,atrick/swift,roambotics/swift,nathawes/swift,stephentyrone/swift,tkremenek/swift,xedin/swift,CodaFi/swift,parkera/swift,jmgc/swift,jmgc/swift,devincoughlin/swift,parkera/swift,shajrawi/swift,lorentey/swift,shajrawi/swift,hooman/swift,atrick/swift,harlanhaskins/swift,CodaFi/swift,xwu/swift,karwa/swift,rudkx/swift,allevato/swift,gribozavr/swift,practicalswift/swift,devincoughlin/swift,rudkx/swift,roambotics/swift,harlanhaskins/swift,gregomni/swift,stephentyrone/swift,jmgc/swift,jmgc/swift,harlanhaskins/swift,gregomni/swift,atrick/swift,aschwaighofer/swift,gribozavr/swift,gregomni/swift,gregomni/swift,tkremenek/swift,parkera/swift,gribozavr/swift,airspeedswift/swift,lorentey/swift,harlanhaskins/swift,benlangmuir/swift,shahmishal/swift,shajrawi/swift,practicalswift/swift,ahoppen/swift,shajrawi/swift,JGiola/swift,xedin/swift,xwu/swift,apple/swift,xedin/swift,apple/swift,lorentey/swift,nathawes/swift,xwu/swift,devincoughlin/swift,sschiau/swift,allevato/swift,sschiau/swift,gregomni/swift,sschiau/swift,airspeedswift/swift,lorentey/swift,karwa/swift,aschwaighofer/swift,xedin/swift,aschwaighofer/swift,lorentey/swift,allevato/swift,tkremenek/swift,allevato/swift,airspeedswift/swift,karwa/swift,CodaFi/swift,rudkx/swift,tkremenek/swift,glessard/swift,gregomni/swift,nathawes/swift,allevato/swift,karwa/swift,roambotics/swift,harlanhaskins/swift,tkremenek/swift,CodaFi/swift,parkera/swift,shahmishal/swift,glessard/swift,atrick/swift,karwa/swift,CodaFi/swift,airspeedswift/swift,aschwaighofer/swift,tkremenek/swift,practicalswift/swift,shajrawi/swift,ahoppen/swift,practicalswift/swift,apple/swift,airspeedswift/swift,shahmishal/swift,practicalswift/swift,apple/swift,jckarter/swift,xedin/swift,xwu/swift,shahmishal/swift,atrick/swift,benlangmuir/swift,benlangmuir/swift,benlangmuir/swift,hooman/swift,lorentey/swift,sschiau/swift,nathawes/swift,shahmishal/swift,JGiola/swift,shahmishal/swift,jmgc/swift,shajrawi/swift,sschiau/swift,jmgc/swift,airspeedswift/swift,stephentyrone/swift,parkera/swift,roambotics/swift,devincoughlin/swift,xwu/swift,aschwaighofer/swift,allevato/swift,sschiau/swift,devincoughlin/swift,ahoppen/swift,gribozavr/swift,harlanhaskins/swift,xwu/swift,devincoughlin/swift,karwa/swift,stephentyrone/swift,benlangmuir/swift,jckarter/swift,CodaFi/swift,nathawes/swift,hooman/swift,hooman/swift,glessard/swift,devincoughlin/swift,jckarter/swift,xedin/swift,roambotics/swift,aschwaighofer/swift,devincoughlin/swift