Make lib/charset.alias a file only provided by converters/libiconv
Create a new USES: charsetfix, that will modify in post patch the Makefile.in to prevent a port from modifying/overwritting the charset.alias file during make install.
Prevent devel/gettext from installing that files.
Fix a couple of ports that actually touch charset.alias during the build phase.
Based on a patch by ale (http://lists.freebsd.org/pipermail/freebsd-gnome/2012-October/027747.html)
Approved by: kwm (gnome)
Exp-run by: miwi
