cran2deb: use iconv(1) to convert debian/{control,changelog,copyright} to utf8

cran2deb: use iconv(1) to convert debian/{control,changelog,copyright} to utf8

lintian(1) likes these files to be utf8.  R does not specify a character
set, so this code just hopes that iconv(1) will do the right thing.  In
the only case where it matters so far (lspls) this allows the package to
build and pass lintian(1).

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/cran2deb@18 edb9625f-4e0d-4859-8d74-9fd3b1da38cb