base: provide `localtime_r` for Windows
base: provide `localtime_r` for Windows

Windows does not have a definition for `localtime_r`.  Simply provide a
wrapper for `localtime` as there is no state that needs to be preserved
to make this function re-entrant safe.

apple/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation,apple/swift-corelibs-foundation,parkera/swift-corelibs-foundation,parkera/swift-corelibs-foundation,apple/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation,e78l/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,parkera/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation