ia32: Change 'match_upconv' to 'match_zero_ext' in 'gen_popcount()'.
ia32: Change 'match_upconv' to 'match_zero_ext' in 'gen_popcount()'.

'match_upconv' might sign-extend, which is wrong for doing a popcount.

MatzeB/libfirm,MatzeB/libfirm,libfirm/libfirm,MatzeB/libfirm,libfirm/libfirm,MatzeB/libfirm,libfirm/libfirm,MatzeB/libfirm,libfirm/libfirm,MatzeB/libfirm,libfirm/libfirm,MatzeB/libfirm