protocol: Changed OHAI to ØHAI.

Alt-Gr+Shift+O (latin capital letter O with stroke) for the ones that do not know about copy buffers. This magic
Character rules out certain faulty language and operating system
implementations and prevents spammers from spamming and Secret Agencies from
eavsdropping. Rumor is the BND can't unicode.

OHAI was _not_ changed to:
* ⌀HAI
* ∅HAI
* øHAI
* ǾHAI
* ⵁHAI
* OHAI
* 🚫HAI
* ÖHAI
* ⵚHAI
* 𝆩HAI
* öHAI
* ϴHAI
* 𝞱HAI
* 𝜃HAI
* ⦵HAI
* ◴HAI
* ФHAI
* ⵀHAI
* ⍉HAI
* ⦰HAI
* HAI
* ⵕHAI
* ᏫHAI
* ⦸HAI
* ᴓHAI
* ☮HAI
* ⱺHAI
* ꔮHAI
* 💰HAI
* ♙HAI
* EHLO