add alphaValue property... although we don't use it anyway it helps to compile stuff

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/gui/trunk@38840 72102866-910b-0410-8b05-ffd578937521

Headers/AppKit/NSView.h

@@ -119,6 +119,7 @@ PACKAGE_SCOPE
   NSInteger _gstate;
   void *_nextKeyView;
   void *_previousKeyView;
+  CGFloat _alphaValue;
 
 @public
   /*
@@ -228,6 +229,15 @@ PACKAGE_SCOPE
 - (BOOL) isRotatedFromBase;
 - (BOOL) isRotatedOrScaledFromBase;
 
+/*
+ * View Layers
+ */
+
+#if OS_API_VERSION(MAC_OS_X_VERSION_10_5, GS_API_LATEST)
+- (CGFloat) alphaValue;
+- (void) setAlphaValue: (CGFloat)alpha;
+#endif
+
 /*
  * Converting Coordinates
  */