Squashed commit of the following:

Fix for #5266 and #5159 - character encodings
    `chmatch` and joins on character columns now work as expected on different encodings as well.

Updated 'fcast' + minor edits to 'fmelt'
    'fcast' updated to handle recent changes to 'fastorder' (used internally) + minor renaming to fmelt functions.

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/datatable@1091 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
+ 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+ssh://svn.r-forge.r-project.org/svnroot/datatable@1092 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Merge branch 'refs/heads/r-forge-git-svn-local'