Add opennssl conf

[lo1ol]

Hello,

I'm working in company which develop Rutoken smart cards. Recently, I got the task to setup stunnel on android with auth using Rutoken. So, I've chose your application as the base for my implementation. I've added possibility to use openssl engines (including the engines for working with smart cards) and set up openssl config file directly in your app.

If you are interesting in the possibility to use openssl engines in your app, then you may merge my branch.

[comp500]

I'm actually working on making stunnel run as a native library rather than as an executable, so that it can be more tightly integrated with the app, and so it works with Android API 29 (which adds restrictions on where you can execute files). This should allow for more complex authentication mechanisms, although you'll probably need to rewrite this PR a bit when I'm done.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 2 weeks if no further activity occurs. Thank you for your contributions.

[comp500]

I'm still working on this, just rather busy currently

[comp500]

I've realised I don't really have the time to maintain this project, nor do I have much use for it myself anymore, but thanks for the PR!