Update UUID to take advantage of SE-0205

This updates UUID to use withUnsafePointer for lets

Author: benasher44

Darwin/Foundation-swiftoverlay/UUID.swift

@@ -62,8 +62,7 @@ public struct UUID : ReferenceConvertible, Hashable, Equatable, CustomStringConv
     /// Returns a string created from the UUID, such as "E621E1F8-C36C-495A-93FC-0C247A3E6E5F"
     public var uuidString: String {
         var bytes: uuid_string_t = (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
-        var localValue = uuid
-        return withUnsafeMutablePointer(to: &localValue) {
+        return withUnsafePointer(to: uuid) {
             $0.withMemoryRebound(to: UInt8.self, capacity: 16) { val in
                 withUnsafeMutablePointer(to: &bytes) {
                     $0.withMemoryRebound(to: Int8.self, capacity: 37) { str in
@@ -76,8 +75,7 @@ public struct UUID : ReferenceConvertible, Hashable, Equatable, CustomStringConv
     }
 
     public var hashValue: Int {
-        var localValue = uuid
-        return withUnsafeMutablePointer(to: &localValue) {
+        return withUnsafePointer(to: uuid) {
               $0.withMemoryRebound(to: UInt8.self, capacity: 16) {
                   return Int(bitPattern: CFHashBytes($0, CFIndex(MemoryLayout<uuid_t>.size)))
               }