New version of dataframe package

[Tim Hesterberg]

There is a new version of the dataframe package, 2.7.1, at
https://sites.google.com/a/timhesterberg.net/www/r-packages

This is for R versions 2.15.1 - 2.15.3.
It includes updates in R's code through 2.15.3.
It takes advantages of changes in R 2.15.1, to make fewer copies
of objects when modifying attributes.

This will not go on CRAN - new CRAN policies prohibit .Call calls to
routines internal to R; this makes it impossible to replace existing
R routines like [.data.frame in a package placed on CRAN.

This will not work with R 3.0.