This is "gopkg.in/veandco/go-sdl2.v0" content with "github.com/veandco/..." replaced by "quesfera/externals/veandco/..."
in import paths within gfx, img, mix, ttf sub-packages.
Therefore go-sdl2 changes on gopkg.in and/or github.com won't affect this 'local' version.
"assets" and "examples" were removed too, because they are not required at compilation.
