- removed identical is_downconv() - used new ia32_skip_downconv() - add ia32_prefix to global function
- removed identical is_downconv()
- used new ia32_skip_downconv()
- add ia32_prefix to global function

[r16234]

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