Code cosmetics (untested yet for regressions!)

+ Made $this->version a define (VERSION).
+ Made $this->errors really static (self::$errors).
+ Moved encodeAsciiToChar() out from the class to the namespace root as a general utility fn.
+ Moved getGif to the "public" section (and removed the Getter/Setter section).
+ Moved reset() closer up to the ctor.
+ Changed comments here & there.
+ Changed the error messages slightly (those might get removed anyway, though).
+ Whitespaces: fixed some tab/space mismatch etc.