Blender Git Loki

Cocoa: Fix missing key window after closing "About"

The cause of this issue goes deeper inside of the custom nature of
the event loop. In short, when not using [NSApp run] closing "About"
window does not make previous key window a key again.

The solution is quite similar to other projects, but we only force
key window from handler when closing one appears to be "About" window.
In all other cases we leave it up to Blender's window manager to make
decision and do not interfere with it.

Test plan:
- Open Blender application
- Go to Blender -> About Blender menu item
- Close About window
- Note that Blender's window does not become active again.

Reviewers: brecht

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D4534