amd64: Added Conv handling. Fixed %rax handling for variadic function calls.
amd64: Added Conv handling. Fixed %rax handling for variadic function calls.

[r27673]

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