SSL_CTX for client; bug fixes
- [API] Allow use of ea_get_ssl_ctx() on the client (optional). PR #186.
- [BUGFIX] Expand datagram with ack-eliciting Initial to 1200 bytes after connection promotion.
- [BUGFIX] Discard CRYPTO frames from lower encryption levels after connection promotion.
- [BUGFIX] Cancel path response if path could not be initialized.