amd64: Use 'mov_imm' instead of 'xor_0' to make a constant 0 during instruction selection.
amd64: Use 'mov_imm' instead of 'xor_0' to make a constant 0 during instruction selection.

Using 'xor' instead is better left to the peephole optimization pass later on.

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