gnu: mesa: Propagate input.

* gnu/packages/gl.scm (mesa): Propagate input libx11.

gnu: gl: Correct copyright notice.
* gnu/packages/gl.scm: Add copyright notice for mesa, moved here from
    module xorg in commit 200726e.

gnu: mesa: Move out of xorg.scm and into gl.scm

* gnu/packages/xorg.scm (mesa): Move to...
* gnu/packages/gl.scm (mesa): ... here.  New variable.
* gnu/packages/gnome.scm, gnu/packages/gnuzilla.scm,
  gnu/packages/qemu.scm, gnu/packages/qt.scm: Adjust accordingly.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

Update references from Guy's old name

gnu: Add freeglut, glu, and FTGL.

* gnu/packages/gl.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>