opengl-core 2.0.1

- Slightly tweaked ruby version requirements that'll have no effect
  until Ruby 3.0, probably.

- Missing attribution added for the bit of platform detection code in
  the Fiddle symbol loader.

opengl-core 2.0.0

- C extensions removed.

- Gl module is now GL. You can easily undo this by adding 'Gl = GL'
  somewhere in your code, but I figure it's probably saner to use GL at
  this point.

- All aux/ types and functions are removed. These are part of the
  opengl-aux gem, now found at https://github.com/nilium/opengl-aux

  opengl-core is now 100% raw bindings.

- The symbol loader can be swapped out with another, so if Fiddle isn't
  your bag, you can replace it by changing GL::GLSym.loader to a
  different loader class. See the comment on GLSym for more info about
  what a symbol loader must implement and see FiddleSymbolLoader for
  what is the only implementation currently available.

- Using a method that isn't implemented will now raise NoMethodError
  upon attempting to load it. load_all_gl_commands! will swallow this
  exception, though I'm not sure it's a great idea to use that when it
  increases the amount of loaded methods to look up when calling a GL
  function.

- Use - instead of _ in file paths.

This simplifies a lot of the code and allows me to keep maintenance of
the auxiliary and the OpenGL bindings separate. In other words, this
can get updated and you _probably_ don't have to worry about breaking
changes to aux types anymore, because the breaking changes to those
will happen to another gem.

Instead, this gem should _only_ be updated with the addition of new
symbol loaders and GL spec updates.

Version 1.3.1

Fixes Texture#unbind -- target argument now optional.

Version 1.3.0

Incremented because the GL commands/enums were updated for GL 4.4.

Version 1.2.0

AKA version pretend-version-1.1.0-never-happened.

Increment to version 1.0.0

Renaming the gem being a breaking change, that's more or less what has
to be done.

Fix module methods for Gl module.

No longer uses GlEnums/GlCommands modules.

GL functions are now wrapped so that they can be overridden if need be.
This will probably be necessary just to ruby-ify some bits of the API.