"unset ytics" in gnuplot 4.2.3 mirrored tics drawn

[John W. Eaton]

On  1-Apr-2008, Shai Ayal wrote:

| Merging now might be premature -- we are still missing text support.
| This is the only big feature still missing from the OpenGL backend.

Does it matter?  It's not like we would be releasing it, and even if
it were to the point of release, I think it may still be experimental
for 3.1.  We would keep the gnuplot backend as the default.

jwe