Fix typo: SeperateAttribs -> SeparateAttribs

[kranich]

I submitted a pull request #76 to that end.

[svenpanne]

To make the transition a bit smoother and avoid a major version bump, can we please keep the old SeperateAttribs constructor, too? Just add the correctly spelled constructor and a deprecation pragma like:

{-# DEPRECATED SeperateAttribs "Use 'SeparateAttribs' instead." #-}

After a few releases I'll remove the old constructor and bump the major version then. GLUT had a similar issue, BTW: haskell-opengl/GLUT@3e4baea

[kranich]

OK, just implemented your suggestions.

[kranich]

Build passed. You can merge pull request #76.

[svenpanne]

Done. Thanks for the fix!