Handle kept memory Phis appropriately.
Handle kept memory Phis appropriately.

This fixes opt/fehler277.c.

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