- Add an --enable-rsyslog option to configure.ac.
- Add a few missing `WOLFSSL_ERROR` calls that were expected by rsyslog unit
tests.
- Add better documentation around `WOLFSSL_SHUTDOWN_NOT_DONE` and define it to
be 0 (rather than 2) when `WOLFSSL_ERROR_CODE_OPENSSL` is defined. This is in
accordance with OpenSSL documentation. Without this change, rsyslog was
failing to do the bidirectional shutdown properly because it was checking the
shutdown return value against 0. I'm keeping the old value when
`WOLFSSL_ERROR_CODE_OPENSSL` isn't defined because it's part of the public
wolfssl interface (it's in ssl.h).
bbb514fa6d