Implement HTTPS for non-linux OSes

[skmp]

TODO

• HTTPS for android (via JNI?)
• HTTPS for windows (via WinHTTP?)
• HTTPS for OSX (would curl work for us? is there some better native alternative?)

Follow up from #1878

[einsteinx2]

@skmp If there is no cross platform c++ lib for this and we're using #ifdefs for platform specific code, we can just use standard Foundation library in a separate Objective-C file for this on Mac, but expose it as a C function. That way we can use the standard NSURLSession or NSURLConnection classes which make it super easy.

Or maybe implement this as another os_ function like other platform specific stuff then I can just implement it, but it depends on what functionality you need and if the function signature can be the same for all platforms.