Fixed subtle issue when optimizing CopyB after Store.
Fixed subtle issue when optimizing CopyB after Store.

We cannot delete the Store if its address aliases with the source of the
CopyB.

This fixes opt/loadstore3.c.

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