Remove dependency on internal OpenSSL test harness

[baentsch]

Some tests depend on ssltestlib, an OpenSSL internal test library. This dependency causes issues when testing in a setup without this code present (non-master source, binary-only).

This issue is to suggest removing this dependency and to develop independent tests providing similar functionality.

[mouse07410]

Perhaps, just copying test/helpers/ssltestlib.c to this repo with the appropriate patch...? it does seem to include some internal headers though...

[baentsch]

Yup -- it has many (internal) dependencies -- that further change between versions. Not in option in my eyes. Testing using just the official, external OpenSSL APIs surely is possible -- just "a bit of work"... :)