tokudb packages for centos6 and other older distributions

Currently we only provide tokudb packages for distributions where we can build TokuDB and TokuKV. The latter requires fairly recent gcc (4.7+) and cmake (2.8.9+).

We should also provide TokuDB for older distributions. One possible approach could be to use TokuKV libraries built on newer distributions. That is, we build everything on, say, fedora18. As an extra step, TokuKV static libraries are uploaded to some known location. On CentOS6 the build downloads these libraries, instead of building them.

Another possibility is using devtoolset