improved detection of pure and const functions (now works for recursive one of any depth)
improved detection of pure and const functions (now works for recursive one of any depth)

[r17002]

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