glDeleteTextures previously did not check that the texture name was
allocated by glGenTextures before adding it to the free texture name
list.
This means that if you delete a texture twice in a row, the name will
appear twice in the free texture list, making glGenTextures return the
same texture name twice in a row.
Each LibGL test can now be tested against a reference QOI image.
Initially, these images can be generated by setting `SAVE_OUTPUT` to
`true`, which will save a bunch of QOI images to `/home/anon`.
At the moment we just check if we *can* render a simple triangle, we do
not yet actually test if the image is indeed the triangle we wanted.
This test also outputs the rendered image when GL_DEBUG is enabled to a
file called "picture.bmp" for manual verification.
Co-authored-by: sunverwerth <s.unverwerth@serenityos.org>
