This came up during code review in https://golang.org/cl/171025.
Backport the improvements to the upstream copies of those packages.

These are better names for these Go packages. The previous names were
an attempt at leveraging the familiarity with Apple's API prefixes
(i.e., AppKit identifiers tend to have "NS" prefix, Core Animation API
identifiers tend to have "CA" prefixes). However, that isn't as useful
here because those prefixes are not very consistent or recognizable
when turned into Go package names.

Create a helper to convert from bool to C.BOOL and use it instead of
more verbose switches. Other people seem to like this style better.

It has become unnecessary after the switch from GLFW v3.2 to v3.3,
because Window.GetCocoaWindow now returns unsafe.Unsafe directly.

It has been released recently. Start using it.

Updates https://github.com/go-gl/glfw/pull/256

Get the ContentView right away, instead of going through cocoaWindow.
The ContentView is all that's needed from cocoaWindow at this time.
This is simpler and reads better.

This way, executing it with -help flag prints usage, rather than
running unconditionally.

Remove an unhelpful blank line.