SFML

Fixing issue with already defined targets, silently return instead of error

Updated the copyright year to 2019

Allow creation of a window without an OpenGL context in order to support use cases where the user wants to render using other graphics APIs.

Fixed EGL incorrectly being passed the anti-aliasing level as EGL_SAMPLE_BUFFERS instead of EGL_SAMPLES. Fixes #1533.

Make sure setActive(false) is called before the surface is destroyed in EglContext. Fixes #1530.