use the proper initializer for Locale in NSHTTPCookie

Author: phausler

Foundation/NSHTTPCookie.swift

@@ -259,7 +259,7 @@ open class HTTPCookie : NSObject {
                 _expiresDate = date
             } else if let dateString = expiresProperty as? String {
                 let formatter = DateFormatter()
-                formatter.locale = Locale(localeIdentifier: "en_US_POSIX")
+                formatter.locale = Locale(identifier: "en_US_POSIX")
                 formatter.dateFormat = "EEE, dd MMM yyyy HH:mm:ss O"   // per RFC 6265 '<rfc1123-date, defined in [RFC2616], Section 3.3.1>'
                 let timeZone = TimeZone(abbreviation: "GMT")
                 formatter.timeZone = timeZone

TestFoundation/TestNSHTTPCookie.swift

@@ -156,7 +156,7 @@ class TestNSHTTPCookie: XCTestCase {
         let cookies =  HTTPCookie.cookies(withResponseHeaderFields: header, forURL: URL(string: "http://example.com")!)
         XCTAssertEqual(cookies[0].domain, "http://example.com")
         let formatter = DateFormatter()
-        formatter.locale = Locale(localeIdentifier: "en_US_POSIX")
+        formatter.locale = Locale(identifier: "en_US_POSIX")
         formatter.dateFormat = "EEE, dd MMM yyyy HH:mm:ss O"
         formatter.timeZone = TimeZone(abbreviation: "GMT")
         if let expiresDate = formatter.date(from: "Wed, 21 Sep 2016 05:33:00 GMT") {