cleanup dead code

git-svn-id: http://svn.mkgmap.org.uk/mkgmap/trunk@2733 25d90789-57f7-4ee0-8453-03a3dfeeeb22
remove code for frig-roundabouts option. At least since r1049 the code 
did nothing useful and is probably not used by anybody as it requires 
the --x-... trick to be used.

git-svn-id: http://svn.mkgmap.org.uk/mkgmap/trunk@2734 25d90789-57f7-4ee0-8453-03a3dfeeeb22