should GLCreateContext use a *Window receiver?

[jackmott]

I expected to be able to call window.GLCreateContext() as other functions follow that pattern, but currently it is sdl.GLCreateContext(window)

[malashin]

Hi @jackmott

I've merged the following changes into the Master branch. Thank you for bringing this up.

• GLCreateContext(), GLMakeCurrent(), GLGetDrawableSize(), GLSwapWindow() are now methods of Window
• Renamed GLSwapWindow() to GLSwap()

func (window *Window) GLCreateContext() {}
func (window *Window) GLMakeCurrent(glcontext GLContext) {}
func (window *Window) GLGetDrawableSize() {}
func (window *Window) GLSwap() {}