[test] add tests of String-from-C-string inout conversion overloads
[test] add tests of String-from-C-string inout conversion overloads

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