Add glfwInitHint

This allows setting hints that control how the library is initialized,
transforming more compile-time options into run-time ones.

docs/context.dox

@@ -84,10 +84,9 @@ objects are recommended for rendering with such contexts.
 You should still [process events](@ref events) as long as you have at least one
 window, even if none of them are visible.
 
-@macos The first time a window is created the menu bar is populated with
-common commands like Hide, Quit and About.  This is not desirable for example
-when writing a command-line only application.  The menu bar setup can be
-disabled with a [compile-time option](@ref compile_options_osx).
+@macos The first time a window is created the menu bar is created.  This is not
+desirable for example when writing a command-line only application.  Menu bar
+creation can be disabled with the @ref GLFW_COCOA_MENUBAR init hint.
 
 
 @subsection context_less Windows without contexts