winbuild: add initial wolfSSL support

[vszakats]

Ref: https://datagirl.xyz/posts/wolfssl_curl_w2k.html

[vszakats]

@jay: I don't mean to test it with wolfSSL. It probably "should" work, or if not, someone using it can report any issue. But I have no way to run this script to verify if I made a silly mistake that breaks it.

[vszakats]

But, according to AppVeyor CI, there is no trivial typo in this PR and existing builds continue to work: https://ci.appveyor.com/project/curlorg/curl/builds/50776650

[jay]

It should be confirmed working before it is added, that said the code looks ok

[vszakats]

I'd say it's good as an initial implementation and straighforward enough that it "just works". The same change has been added and tested earlier in Makefile.mk. It's basically a copy-paste change with include, lib and wolfssl.lib set compared to e.g. mbedTLS.

One setting that may or may not be necessary is -DSIZEOF_LONG_LONG=8. It seemed necessary a few years ago to avoid a build issue within a wolfSSL header. Also with CMake, but our CI builds never needed that.
curl/curl-for-win@04f3a9c

Chances are good this setting is no longer needed. In any case if it's an issue, someone will likely report it.