patch 9.1.0656: MS-Windows: MSVC Makefile CPU handling can be improved

patch 9.1.0656: MS-Windows: MSVC Makefile CPU handling can be improved

Problem:  MS-Windows: MSVC Makefile CPU handling can be improved
Solution: Update Makefile and also remove some old code
          (Ken Takata)

* The variable `ASSEMBLY_ARCHITECTURE` was originally used to generate
  the manifest file. However, this was removed in v7.0.198.  Remove
  `ASSEMBLY_ARCHITECTURE` and use `CPU` instead.
* `/arch:AVX512` is available starting from Visual C++ 2017.
* ARM64 was not considered when validating CPUNR.
  Skip the validation for ARM64 for now.
* Remove old code for VC6/7 and Win9x.

closes: #15422

Signed-off-by: Ken Takata <kentkt@csc.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>