Log Message:
Import glfw-3.1.2 as graphics/glfw.
Originally packaged in pkgsrc-wip by ryoon@ and then updated by nros@ and
myself.

GLFW is a free, Open Source, multi-platform library for creating
OpenGL contexts and managing input, including keyboard, mouse,
joystick and time. It is intended to be simple to integrate into
existing applications and does not lay claim to the main loop.

GLFW has native support for Windows, Mac OS X and many Unix-like
systems using the X Window System, such as Linux and FreeBSD.

GLFW is licensed under the zlib/libpng license.