Outputs minimum-redundancy length-limited code bitlengths for symbols with the

given counts. The bitlengths are limited by maxbits.



The output is tailored for DEFLATE: symbols that never occur, get a bit length

of 0, and if only a single symbol occurs at least once, its bitlength will be 1,

and not 0 as would theoretically be needed for a single symbol.



frequencies: The amount of occurances of each symbol.

n: The amount of symbols.

maxbits: Maximum bit length, inclusive.

bitlengths: Output, the bitlengths for the symbol prefix codes.

return: 0 for OK, non-0 for error.