Cocoa: Fix full screen window iconification

Iconification (miniaturization) of undecorated windows stopped working
unless the window has the NSWindowStyleMaskMiniaturizable style.

src/cocoa_window.m

@@ -35,15 +35,14 @@
 //
 static NSUInteger getStyleMask(_GLFWwindow* window)
 {
-    NSUInteger styleMask = 0;
+    NSUInteger styleMask = NSWindowStyleMaskMiniaturizable;
 
     if (window->monitor || !window->decorated)
         styleMask |= NSWindowStyleMaskBorderless;
     else
     {
         styleMask |= NSWindowStyleMaskTitled |
-                     NSWindowStyleMaskClosable |
-                     NSWindowStyleMaskMiniaturizable;
+                     NSWindowStyleMaskClosable;
 
         if (window->resizable)
             styleMask |= NSWindowStyleMaskResizable;