+ iradix changed from 3-pass 11bit to 4-pass 8bit,  added radix skipping, memset skipping and large comment block.
+ iradix hooked into fastorder and qsort removed.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/datatable@1092 edb9625f-4e0d-4859-8d74-9fd3b1da38cb