[R-pkgs] plotrix v2.6-4

[Jim Lemon]

Hi all,
After a lot of rewriting, I am happy to say that plotrix_2.6-4 is on 
CRAN. The reason I am announcing this is that the newish hierobarp 
function has had a complete rewrite. This was the result of my learning 
that the old version was horrendously slow on large data sets. Let me 
know if there are any other problems in the package. Next up - a 
function to center plot titles to the figure region on plots that are 
way off center.

Jim