added visited flag to detect endless memory loops in unreachable code, else the optimizer would fall into an endless loop...
added visited flag to detect endless memory loops in unreachable code,
else the optimizer would fall into an endless loop...

[r6694]

killbug2004/libfirm,MatzeB/libfirm,davidgiven/libfirm,8l/libfirm,jonashaag/libfirm,killbug2004/libfirm,davidgiven/libfirm,jonashaag/libfirm,killbug2004/libfirm,MatzeB/libfirm,killbug2004/libfirm,8l/libfirm,killbug2004/libfirm,jonashaag/libfirm,MatzeB/libfirm,libfirm/libfirm,davidgiven/libfirm,jonashaag/libfirm,jonashaag/libfirm,libfirm/libfirm,MatzeB/libfirm,jonashaag/libfirm,davidgiven/libfirm,jonashaag/libfirm,davidgiven/libfirm,davidgiven/libfirm,libfirm/libfirm,killbug2004/libfirm,8l/libfirm,8l/libfirm,MatzeB/libfirm,8l/libfirm,libfirm/libfirm,libfirm/libfirm,davidgiven/libfirm,killbug2004/libfirm,MatzeB/libfirm,8l/libfirm,8l/libfirm,MatzeB/libfirm