[Foundation] Implemented rename

Author: Bouke

Sources/Get/PackagesDirectory.swift

@@ -10,7 +10,7 @@
 
 import struct PackageDescription.Version
 import func Utility.mkdir
-import func POSIX.rename
+import func Utility.rename
 import PackageType
 import Utility
 

Sources/POSIX/rename.swift renamed to Sources/Utility/rename.swift

@@ -8,10 +8,8 @@
  See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 */
 
-import var libc.errno
-import func libc.rename
+import Foundation
 
 public func rename(old: String, new: String) throws {
-    let rv = libc.rename(old, new)
-    guard rv == 0 else { throw SystemError.rename(errno, old: old, new: new) }
+    try NSFileManager.`default`().moveItem(atPath: old, toPath: new)
 }

Tests/Functional/ClangModuleTests.swift

@@ -11,7 +11,7 @@
 import struct Utility.Path
 import func Utility.symlink
 import func Utility.walk
-import func POSIX.rename
+import func Utility.rename
 import func Utility.mkdir
 import func POSIX.popen
 import XCTest

Tests/Functional/ValidLayoutTests.swift

@@ -11,7 +11,7 @@
 import struct Utility.Path
 import func Utility.symlink
 import func Utility.walk
-import func POSIX.rename
+import func Utility.rename
 import func Utility.mkdir
 import func POSIX.popen
 import XCTest