Add self-tests at startup #4081

The idea would be to test basic sanity of the execution environment and dependencies. for example:

• check std::list and the functions overridden in the compatibility wrappers for older glibc/glibc++
• test basic secp256k operations
• test hash functions

This idea was brought up by @sipa in issue #4042. The tests should run very quickly (<0.1 second).

Implemented by #4339

@laanwj what about libsecp256k and the hash functions?

Sure, you could do that... (but the prime motivation here was to do this because these operations were performed by external libraries - now that secp256k1 is internal, and the hash functions are also performed by our own code, I'm not sure what kind of errors it is supposed to catch)