HuffmanTable: make nb_syms_ able to store 256 symbols

Right now, we're not using all of the 256 possible symbols,
but with progressive we could. Makeing nb_syms_ be an int will
avoid a future bug.

Also: remove unused BuildHuffmanCodes() declaration.

Author: skal65535

src/sjpegi.h

@@ -137,7 +137,7 @@ extern void SetMinQuantMatrix(const uint8_t* const m, uint8_t out[64],
 struct HuffmanTable {
   uint8_t bits_[16];     // number of symbols per bit count
   const uint8_t* syms_;  // symbol map, in increasing bit length
-  uint8_t nb_syms_;      // cached value of sum(bits_[])
+  int nb_syms_;          // cached value of sum(bits_[])
 };
 
 // quantizer matrices
@@ -276,9 +276,6 @@ struct Encoder {
   // Histogram pass
   void CollectHistograms();
 
-  void BuildHuffmanCodes(const HuffmanTable* const tab,
-                         uint32_t* const codes);
-
   typedef int (*QuantizeBlockFunc)(const int16_t in[64], int idx,
                                    const Quantizer* const Q,
                                    DCTCoeffs* const out, RunLevel* const rl);