configure: explicitly check that OpenGL version is sufficient
configure: explicitly check that OpenGL version is sufficient

Also provide more useful error message, with a link to the wiki entry on
OpenGL and remote display. Fixes #218.

MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3