musl compatibility in net_open_tcp2

[dirtslayer]

Ensure musl compatibility in net_open_tcp2

This PR ensures musl compatibility in net_open_tcp2 by removing multi‑socket
return paths.

The packages required to compile on Alpine are build-base git mk-configure
mk-configure-dev libmaa-dev zlib-dev musl-dev

Changes to net_server.c/net_open_tcp2

0. rtmp renamed to ai

1. getaddrinfo() now uses:

   • ai_family = AF_UNSPEC
   • ai_flags = AI_ADDRCONFIG | AI_V4MAPPED
   • This avoids musl’s EAI_ADDRFAMILY error when an IPv4 literal
     (e.g., "10.x.x.x") is passed with AF_INET6.

2. Added detailed debug logging so socket selection and fallback
   behavior are visible when running with -d.

3. Dual‑stack attempt (IPv6 with IPV6_V6ONLY=0) is still tried,
   but, we fall back to separate IPv4 and IPv6 attempts.

4. dictd cannot safely handle multiple listening
   sockets. The original code returned two sockets when dual‑stack
   failed. This version ALWAYS returns exactly ONE socket:

   • Prefer IPv4 if available
   • Otherwise use IPv6
   • Any unused socket is closed immediately.

Result:

• No BUS ERROR crashes on Alpine/musl
• No out‑of‑bounds access in dictd’s main loop
• No use‑after‑free of the socket array
• avoids dual‑socket return values
• preserves dictd’s original single‑listener design while remaining compatible
  with IPv4 and IPv6

Testing:

./dictd -d nodetach -c /etc/dictd/dictd.conf --listen-to 0.0.0.0 --address-family 4
./dictd -d nodetach -c /etc/dictd/dictd.conf --listen-to localhost --address-family 4
./dictd -d nodetach -c /etc/dictd/dictd.conf --listen-to 127.0.0.1 --address-family 4
./dictd -d nodetach -c /etc/dictd/dictd.conf --listen-to :: --address-family 6
./dictd -d nodetach -c /etc/dictd/dictd.conf --listen-to ::1 --address-family 6