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)
