only set compound_ret flag if it was really a ret and not a parameter
only set compound_ret flag if it was really a ret and not a parameter

[r16033]

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