Fix names of menu keys in options dialog on OS X

Apple changed the implementation of KeyEvent.getKeyText() to
return the unicode for the key glyph instead of a textual
description.
diff --git a/java/com/tigervnc/vncviewer/MenuKey.java b/java/com/tigervnc/vncviewer/MenuKey.java
index 63b6380..071c004 100644
--- a/java/com/tigervnc/vncviewer/MenuKey.java
+++ b/java/com/tigervnc/vncviewer/MenuKey.java
@@ -70,6 +70,13 @@
     return menuSymbols;
   }
 
+  public static String getKeyText(MenuKeySymbol sym) {
+    if (VncViewer.os.startsWith("mac os x"))
+      return sym.name.replace("_", " ");
+    else
+      return KeyEvent.getKeyText(sym.keycode);
+  }
+
   public static String getMenuKeyValueStr() {
     String s = "";
     for (int i = 0; i < getMenuKeySymbolCount(); i++) {
diff --git a/java/com/tigervnc/vncviewer/OptionsDialog.java b/java/com/tigervnc/vncviewer/OptionsDialog.java
index 3bd74e2..1681518 100644
--- a/java/com/tigervnc/vncviewer/OptionsDialog.java
+++ b/java/com/tigervnc/vncviewer/OptionsDialog.java
@@ -412,7 +412,7 @@
     JLabel menuKeyLabel = new JLabel("Menu Key");
     String[] menuKeys = new String[MenuKey.getMenuKeySymbolCount()];
     for (int i = 0; i < MenuKey.getMenuKeySymbolCount(); i++)
-      menuKeys[i] = KeyEvent.getKeyText(MenuKey.getMenuKeySymbols()[i].keycode);
+      menuKeys[i] = MenuKey.getKeyText(MenuKey.getMenuKeySymbols()[i]);
     menuKey  = new JComboBox(menuKeys);
 
     inputPanel.add(viewOnly,