MachMsgType: make it a class, not an enum

The reason is that we will need to read type descriptors even when we don't
know what they are in advance, for instance for deallocating partly read
messages.

mach/MachMsgType.java

@@ -15,22 +15,24 @@
  * read or written. Users are advised to set the buffer's mark before
  * using these methods and restore it if an exception occurs.
  */
-public enum MachMsgType {
-    /* List of types currently in use. Extend as needed. */
-    CHAR(8, 8, true),
-    INTEGER_32(2, 32, false),
-    INTEGER_64(11, 64, false),
-    MOVE_RECEIVE(16, 32, false, true),
-    MOVE_SEND(17, 32, false, true),
-    MOVE_SEND_ONCE(18, 32, false, true),
-    COPY_SEND(19, 32, false, false),
-    MAKE_SEND(20, 32, false, false),
-    MAKE_SEND_ONCE(21, 32, false, false);
-
-    /* Aliases used for received ports. */
-    public static final MachMsgType PORT_RECEIVE = MOVE_RECEIVE;
-    public static final MachMsgType PORT_SEND = MOVE_SEND;
-    public static final MachMsgType PORT_SEND_ONCE = MOVE_SEND_ONCE;
+public class MachMsgType {
+    public static final MachMsgType
+
+        /* List of types currently in use. Extend as needed. */
+        CHAR =              new MachMsgType(8, 8, true),
+        INTEGER_32 =        new MachMsgType(2, 32, false),
+        INTEGER_64 =        new MachMsgType(11, 64, false),
+        MOVE_RECEIVE =      new MachMsgType(16, 32, false, true),
+        MOVE_SEND =         new MachMsgType(17, 32, false, true),
+        MOVE_SEND_ONCE =    new MachMsgType(18, 32, false, true),
+        COPY_SEND =         new MachMsgType(19, 32, false, false),
+        MAKE_SEND =         new MachMsgType(20, 32, false, false),
+        MAKE_SEND_ONCE =    new MachMsgType(21, 32, false, false),
+
+        /* Aliases used for received ports. */
+        PORT_RECEIVE =      MOVE_RECEIVE,
+        PORT_SEND =         MOVE_SEND,
+        PORT_SEND_ONCE =    MOVE_SEND_ONCE;
 
     /* Constants for mach_msg_type_t */
     private static final int BIT_INLINE     = 0x10000000;