removed prefer_fastcall: backends can now decide how to handle mtp_property_private methods
removed prefer_fastcall: backends can now decide how to handle mtp_property_private methods

[r14627]

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