fix decode_buffer parsing gb2312 under specific conditions

[dockfries]

This pr attempts to fix #328 under specific conditions, but no matter what, there is still no optimal solution for short text parsing, and short text is the most easily misjudged.

Test text: "梦幻城v4.2.0" in gb2312 format.

[dockfries]

Well, when we remove the version part in this example, it will still be parsed as euc-kr.
The best solution is to use long text, so I don't think there is a fundamental solution to this issue.

Old Samp client displayed normally, because the hostname and gamemodetext ... were displayed based on the actual Windows region, which also means that in other languages, the Windows system would be garbled.

Unless we can let the launcher know what the current server's encoding is for decoding.
For example, SetServerRule("charset", "gb2312"), then after the launcher gets the rules, if there is a "charset" key and value, different from the previous one, decode again...?

But considering different query packet types and backward compatibility, it is difficult.