Fix #33800: GLSL group nodes not using the external input value unless a node
was connected to the socket.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53814 954f8c5b-7b00-dc11-b283-0030488c597c
Code cleanup: remove some remaining code from the old compositor.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53815 954f8c5b-7b00-dc11-b283-0030488c597c