Rework building: Windows changes to handle extensions and product names

Add platform::Windows, which is a generic Windows module, and
platform::Windows::MSVC, which is a module specifically for MS Visual
C.

This reworks Configurations/windows-makeffile.tmpl to work out product
names in platform::Windows.  Something to be noted is that the new
functionality ignores the *_extension config attributes, as they were
never used.

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/7473)