Returns a string, in character format, that represents
hexstring converted
to character. The returned string has half as many bytes as the original
hexstring.
hexstring can be of any length. If
necessary, it is padded with a leading zero to make an even number
of hexadecimal digits.
You can optionally include whitespace characters in
hexstring (at byte boundaries
only, not leading or trailing) to improve readability; they are ignored.
If hexstring is null, the function
returns a null string.
