[stdlib] Simplify implementation of string-to-integer parsing.
[stdlib] Simplify implementation of string-to-integer parsing.

apple/swift,benlangmuir/swift,atrick/swift,tkremenek/swift,gregomni/swift,roambotics/swift,hooman/swift,rudkx/swift,apple/swift,JGiola/swift,atrick/swift,glessard/swift,JGiola/swift,roambotics/swift,xwu/swift,xwu/swift,rudkx/swift,benlangmuir/swift,ahoppen/swift,parkera/swift,tkremenek/swift,glessard/swift,glessard/swift,xwu/swift,roambotics/swift,JGiola/swift,ahoppen/swift,tkremenek/swift,ahoppen/swift,benlangmuir/swift,xwu/swift,glessard/swift,ahoppen/swift,xwu/swift,rudkx/swift,parkera/swift,parkera/swift,benlangmuir/swift,rudkx/swift,roambotics/swift,benlangmuir/swift,hooman/swift,parkera/swift,JGiola/swift,parkera/swift,apple/swift,parkera/swift,xwu/swift,apple/swift,glessard/swift,parkera/swift,JGiola/swift,rudkx/swift,gregomni/swift,gregomni/swift,hooman/swift,tkremenek/swift,gregomni/swift,roambotics/swift,rudkx/swift,apple/swift,xwu/swift,ahoppen/swift,gregomni/swift,glessard/swift,atrick/swift,ahoppen/swift,hooman/swift,atrick/swift,benlangmuir/swift,roambotics/swift,tkremenek/swift,JGiola/swift,tkremenek/swift,gregomni/swift,parkera/swift,atrick/swift,apple/swift,atrick/swift,hooman/swift,tkremenek/swift,hooman/swift,hooman/swift