[HOpenGL] Patches to cabal files

Hello, I had a hard time finding the source for the opengl bindings because the locations mentioned in the .cabals were no longer valid. In particular, http://www.haskell.org/HOpenGL/ is a 404. Eventually I stumbled on the wiki page, so I changed the above URL to http://www.haskell.org/haskellwiki/Opengl and added a link to the darcs repo in each cabal file. Also, 'cabal sdist' gave a few warnings and one error so I fixed those as well. I've attached patches for all these changes. Please let me know if you have any questions or concerns. Thanks, Jason