[Rd] MBCS support and iconv

[Prof Brian Ripley]

I am considering requiring HAVE_ICONV as part of SUPPORT_MBCS for 2.3.0.
This would require the iconv from glibc or libiconv if multi-byte 
character sets (notably UTF-8) are to be usable.

As far as I know this would only affect commercial Unixen, where libiconv 
could be installed. (We know that Linux, Mac OS X and Windows would be 
unaffected.  I suspect from its man pages that FreeBSD nowadays has 
libiconv installed, despite comments to the contrary in libiconv 
propaganda.) If anyone sees a problem with this, please let me know soon.

This is mainly to simplify support (including documentation) and testing.
There are too many paths through the code, and only that using iconv gets 
more than cursory testing.  Also, problems with wide-char support in some 
OSes are becoming apparent and we can circumvent them by using iconv to do 
conversions.

There are already a number of new internationalization features in 
R-patched/R-devel (thanks in good part to Ei-ji Nakama), including support 
for postscript()/pdf() in non-Latin-1 languages.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595