Disable opengl demo if Qt4 or OpenGL cannot be found. (transplanted from d2657addc177e98abb860ecdbba97c1a092a6e7a)
Disable opengl demo if Qt4 or OpenGL cannot be found.
(transplanted from d2657addc177e98abb860ecdbba97c1a092a6e7a)

cjntaylor/eigen,pthulhu/eigen,pthulhu/eigen,cjntaylor/eigen,pthulhu/eigen,pthulhu/eigen,cjntaylor/eigen,pthulhu/eigen,cjntaylor/eigen