databases/trilogy: Add trilogy 2.6.0

Trilogy is a client library for MySQL-compatible database servers, designed for
performance, flexibility, and ease of embedding.

It's currently in production use on github.com.

Features:
- Supports the most frequently used parts of the text protocol
  - Handshake
  - Password authentication
  - Query, ping, and quit commands
- Support prepared statements (binary protocol)
- Low-level protocol API completely decoupled from IO
- Non-blocking client API wrapping the protocol API
- Blocking client API wrapping the non-blocking API
- No dependencies outside of POSIX, the C standard library & OpenSSL
- Minimal dynamic allocation
- MIT licensed