Please update addaddmul_1msb0.asm to support ABI in mingw64

[Torbjörn Granlund]

Torbjörn Granlund <tg at gmplib.org> writes:

  zen1    2       2         2             =       all equal (saturated mul)

Typo.  The last number should be 4, not 2.

-- 
Torbjörn
Please encrypt, key id 0xC8601622