OSX fixed set cursor position on retina in fullscr.

Weird behavior.

glfwSetCursorPos worked fine in fullscreen if I had monitor connected to the laptop, on either display.
But was offset by about 200px in fullscreen if no monitor was connected.

src/cocoa_window.m

@@ -1058,6 +1058,10 @@ void _glfwPlatformSetCursorPos(_GLFWwindow* window, double x, double y)
         CGDisplayMoveCursorToPoint(window->monitor->ns.displayID,
                                    CGPointMake(x, y));
     }
+    else if ([window->ns.view isInFullScreenMode])
+    {
+        CGWarpMouseCursorPosition(CGPointMake(x, y));
+    }
     else
     {
         const NSRect contentRect = [window->ns.view frame];