fix remove_empty_blocks (don't use a generic walker it will get confused)
fix remove_empty_blocks (don't use a generic walker it will get confused)

[r16393]

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