The constants `NSControlStateValueOn`, `NSControlStateValueOff` and `NSControlStateValueMixed` are only available for macOS 10.13 or above according to https://developer.apple.com/documentation/appkit/nscontrolstatevalueon?language=objc.
Without this commit, compilation fails with this message:
```
glfw/cocoa_window.m:1537:28: error: use of undeclared identifier 'NSControlStateValueOn'
item.state = NSControlStateValueOn;
^
glfw/cocoa_window.m:1539:28: error: use of undeclared identifier 'NSControlStateValueMixed'
item.state = NSControlStateValueMixed;
^
glfw/cocoa_window.m:1542:47: error: use of undeclared identifier 'NSControlStateValueOn'
item.state = controller.isDesired ? NSControlStateValueOn : NSControlStateValueOff;
^
glfw/cocoa_window.m:1542:71: error: use of undeclared identifier 'NSControlStateValueOff'
item.state = controller.isDesired ? NSControlStateValueOn : NSControlStateValueOff;
^
```
To fix this, simply redefine the constants to use the old and now deprecated constants on older macOS versions.
The code that causes this was introduced in 98519bf326834a126e89489a6a221ff21fab100f.