R: Revert update to version 3.1.1

This reverts commit 6e803a684fff2db30f6e10e8dc5a830184a12b9e. The new version
fails its test suite [1]. The issue has been reported upstream [2].

[1] http://hydra.cryp.to/build/191457/nixlog/1/raw
[2] https://bugs.r-project.org/bugzilla/show_bug.cgi?id=15975