[CSSimplify] Allow implicit Swift -> C pointer conversion within optional types
[CSSimplify] Allow implicit Swift -> C pointer conversion within optional types

Support Swift -> C pointer conversions even if argument required
a value to optional promotion or is optional.

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