Aqua Icons support on HiDPI displays.

[Alexander Scherbatiy]

   Hello,

   The GetIconRef method is used in the CImage.m now to get the system 
icons on MacOSX.

   The NSImage + (id)imageNamed:(NSString *)name method can be used 
directly instead.

   There are NSImageNameFolder, NSImageNameFolderBurnable, and 
NSImageNameFolderSmart constants but I can't find
   the constant for the open folder icon.
https://developer.apple.com/library/mac/documentation/cocoa/reference/applicationkit/classes/NSImage_Class/Reference/Reference.html#//apple_ref/doc/constant_group/Toolbar_Named_Images

   The same is for the alert stop system icon. There are NSImageNameInfo 
and NSImageNameCaution icons but I can't find
   the constant for the alert stop icon.

   Where is it possible to get the open folder and stop icons that are 
defined as kOpenFolderIcon and kAlertStopIcon for the GetIconRef method?

   Thanks,
   Alexandr.