don't copy unknowns around in cmovs
don't copy unknowns around in cmovs

[r14919]

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