Cocoa: Finish launching NSApp in glfwInit

This moves the remaining bits of NSApplication initialization into
_glfwPlatformInit.  As a side-effect of this, any command-line program
initializing GLFW will get a menu bar, which is not ideal.

If this has happened to you and a bisect led you here, please see the
GLFW_COCOA_MENUBAR init hint introduced in GLFW 3.3.

If this patch is a terrible idea, please get in touch in the 3.4 release
timeframe.

This is a replacement for 6e6805000a,
which attempts to preserve the existing menu bar creation behavior for
the 3.3-stable branch.

Fixes #1649.

README.md

@@ -148,12 +148,15 @@ information on what to include when reporting a bug.
    (#1623)
  - [Cocoa] Added support for `VK_EXT_metal_surface` (#1619)
  - [Cocoa] Added locating the Vulkan loader at runtime in an application bundle
+ - [Cocoa] Moved main menu creation to GLFW initialization time (#1649)
  - [Cocoa] Removed dependency on the CoreVideo framework
  - [Cocoa] Bugfix: `glfwSetWindowSize` used a bottom-left anchor point (#1553)
  - [Cocoa] Bugfix: Window remained on screen after destruction until event poll
    (#1412)
  - [Cocoa] Bugfix: Event processing before window creation would assert (#1543)
  - [Cocoa] Bugfix: Undecorated windows could not be iconified on recent macOS
+ - [Cocoa] Bugfix: Touching event queue from secondary thread before main thread
+   would abort (#1649)
  - [X11] Bugfix: The CMake files did not check for the XInput headers (#1480)
  - [X11] Bugfix: Key names were not updated when the keyboard layout changed
    (#1462,#1528)