[OutputStream] Rename outputStreamToMemory() to toMemory() to match the Darwin version

Author: ikesyo

Foundation/NSStream.swift

@@ -212,7 +212,7 @@ open class OutputStream : Stream {
         return Stream.Status(rawValue: UInt(CFWriteStreamGetStatus(_stream)))!
     }
 
-    open class func outputStreamToMemory() -> Self {
+    open class func toMemory() -> Self {
         return self.init(toMemory: ())
     }
 

TestFoundation/TestNSStream.swift

@@ -181,7 +181,7 @@ class TestNSStream : XCTestCase {
         var buffer = Array<UInt8>(repeating: 0, count: 12)
         var myString = "Hello world!"
         let encodedData = [UInt8](myString.utf8)
-        let outputStream = OutputStream.outputStreamToMemory()
+        let outputStream = OutputStream.toMemory()
         XCTAssertEqual(Stream.Status.notOpen, outputStream.streamStatus)
         outputStream.open()
         XCTAssertEqual(Stream.Status.open, outputStream.streamStatus)