Add simple name auto-completion for the chat

[MoonPadUSer]

No description provided.

[MoonPadUSer]

Todo: exclude bots from the auto-completion

[ghost]

Things that would block me accept this:

• no sanity check on s: there is no certainty you don't write out of memory thus I consider this code unsafe and not acceptable.

Now, general coding sanity:

• Instead of using if/else that takes the whole function and change indentation, just return at end of if.
• Indentation change found in 2nd patch near like 824, easy to see with a diff.
• lines ending with spaces found
• what is the printf( "start" ...) meant to do in a part of the code you don't touch?
• strlen( foo ) in a loop that never changes foo is slow
• strlen is slow anyway, avoid calling it for nothing (I see at least 1 useless call)

More specific to that current code:

• avoid using the loop macros, use for( auto const& foo : foobar ) or normal macros.
• please stop having for loops and if condition on same line to then use misleading indentation.
• complete() is used only once in the whole code. Take the occasion to have the architecture safer, for example by using an std::string (there are other methods, too)
• for the same reason, there's no point in keeping it's declaration extern or in a header anyway
• avoid using an external structure's variables and literal constants. Instead, add it a method with a name that describes what it does (for example here: 'bool clientstate::is_player(void) const;' and 'char const* clientstate::name(void) const;'

[TheAssassin]

I couldn't spot any apparent potential overflows any more. Good work! Please change these inline comments, I'll try the PR in the meantime.

[TheAssassin]

Inline comments. Please avoid.