HTML5 Events API.

Implements a C-based events library for various HTML5 APIs.

This adds event-based and polling-based API for the following HTML5 APIs:

DOM Level 3 Events, DeviceOrientation, Screen Orientation, Fullscreen, Pointer Lock, Vibration, Page Visibility, Touch and Gamepad.

Not completed yet, I'm still about to do a documentation and cleanup pass of the events.h file, but putting this up already for comments.

Addresses issue #482 and probably others too, like #2027.