make no-poi-address option work again. The real option name
is now --poi-address which is on by default. Use --no-poi-address to
disable. This is how it was before the --no- prefix was made generic.

git-svn-id: http://svn.mkgmap.org.uk/mkgmap/trunk@2517 25d90789-57f7-4ee0-8453-03a3dfeeeb22