Update Windows build instructions
Update Windows build instructions

Update the windows build instructions to account for:
- the new module (WinSDK), the changes in the ICU configuration
- the need for Visual Studio 2017
- the dropped requirement for installing Python, CMake, Ninja as they are part of VS2017
- the fact that the release mode crasher has been fixed
- the fact that swift-corelibs-libdispatch is supported on Windows
- the changes in clang's flags due to updates to clang
karwa/swift,stephentyrone/swift,lorentey/swift,sschiau/swift,nathawes/swift,harlanhaskins/swift,xwu/swift,practicalswift/swift,lorentey/swift,xedin/swift,airspeedswift/swift,stephentyrone/swift,devincoughlin/swift,gregomni/swift,shahmishal/swift,shahmishal/swift,CodaFi/swift,glessard/swift,tkremenek/swift,shahmishal/swift,ahoppen/swift,shahmishal/swift,parkera/swift,apple/swift,gribozavr/swift,karwa/swift,practicalswift/swift,nathawes/swift,roambotics/swift,sschiau/swift,devincoughlin/swift,austinzheng/swift,harlanhaskins/swift,parkera/swift,shahmishal/swift,shahmishal/swift,sschiau/swift,tkremenek/swift,rudkx/swift,amraboelela/swift,nathawes/swift,danielmartin/swift,stephentyrone/swift,parkera/swift,roambotics/swift,allevato/swift,austinzheng/swift,airspeedswift/swift,tkremenek/swift,atrick/swift,sschiau/swift,aschwaighofer/swift,ahoppen/swift,austinzheng/swift,allevato/swift,xedin/swift,nathawes/swift,parkera/swift,ahoppen/swift,apple/swift,danielmartin/swift,hooman/swift,xedin/swift,gribozavr/swift,danielmartin/swift,xedin/swift,parkera/swift,jmgc/swift,gregomni/swift,allevato/swift,jmgc/swift,amraboelela/swift,harlanhaskins/swift,xedin/swift,ahoppen/swift,hooman/swift,xedin/swift,shajrawi/swift,jckarter/swift,lorentey/swift,harlanhaskins/swift,xwu/swift,apple/swift,aschwaighofer/swift,stephentyrone/swift,xwu/swift,roambotics/swift,glessard/swift,airspeedswift/swift,JGiola/swift,rudkx/swift,karwa/swift,aschwaighofer/swift,lorentey/swift,ahoppen/swift,xwu/swift,benlangmuir/swift,sschiau/swift,nathawes/swift,jckarter/swift,tkremenek/swift,karwa/swift,allevato/swift,gribozavr/swift,tkremenek/swift,rudkx/swift,austinzheng/swift,CodaFi/swift,glessard/swift,hooman/swift,danielmartin/swift,danielmartin/swift,CodaFi/swift,benlangmuir/swift,shajrawi/swift,gregomni/swift,hooman/swift,devincoughlin/swift,karwa/swift,amraboelela/swift,shajrawi/swift,glessard/swift,apple/swift,lorentey/swift,airspeedswift/swift,tkremenek/swift,stephentyrone/swift,shajrawi/swift,JGiola/swift,xedin/swift,practicalswift/swift,aschwaighofer/swift,CodaFi/swift,gribozavr/swift,amraboelela/swift,xwu/swift,jmgc/swift,karwa/swift,amraboelela/swift,practicalswift/swift,gregomni/swift,karwa/swift,benlangmuir/swift,practicalswift/swift,roambotics/swift,shajrawi/swift,roambotics/swift,allevato/swift,atrick/swift,parkera/swift,karwa/swift,sschiau/swift,shajrawi/swift,amraboelela/swift,jckarter/swift,jckarter/swift,rudkx/swift,jckarter/swift,gribozavr/swift,stephentyrone/swift,airspeedswift/swift,apple/swift,lorentey/swift,nathawes/swift,xwu/swift,gribozavr/swift,shahmishal/swift,apple/swift,jmgc/swift,danielmartin/swift,harlanhaskins/swift,amraboelela/swift,atrick/swift,sschiau/swift,rudkx/swift,allevato/swift,austinzheng/swift,practicalswift/swift,harlanhaskins/swift,devincoughlin/swift,rudkx/swift,gribozavr/swift,austinzheng/swift,parkera/swift,sschiau/swift,austinzheng/swift,shajrawi/swift,devincoughlin/swift,gregomni/swift,hooman/swift,glessard/swift,aschwaighofer/swift,devincoughlin/swift,aschwaighofer/swift,nathawes/swift,benlangmuir/swift,hooman/swift,harlanhaskins/swift,airspeedswift/swift,hooman/swift,CodaFi/swift,devincoughlin/swift,ahoppen/swift,jmgc/swift,JGiola/swift,practicalswift/swift,gregomni/swift,atrick/swift,devincoughlin/swift,stephentyrone/swift,jmgc/swift,xwu/swift,lorentey/swift,danielmartin/swift,shajrawi/swift,atrick/swift,aschwaighofer/swift,jckarter/swift,allevato/swift,shahmishal/swift,benlangmuir/swift,jckarter/swift,gribozavr/swift,xedin/swift,practicalswift/swift,roambotics/swift,parkera/swift,CodaFi/swift,JGiola/swift,JGiola/swift,glessard/swift,JGiola/swift,tkremenek/swift,lorentey/swift,jmgc/swift,CodaFi/swift,atrick/swift,airspeedswift/swift,benlangmuir/swift