* sysdeps/x86_64/add_n.S: New file.
* sysdeps/x86_64/addmul_1.S: New file.
* sysdeps/x86_64/lshift.S: New file.
* sysdeps/x86_64/mul_1.S: New file.
* sysdeps/x86_64/rshift.S: New file.
* sysdeps/x86_64/sub_n.S: New file.
* sysdeps/x86_64/submul_1.S: New file.