Fixed wrong return type of token_base::get_token()

Author: Huang-Ming Huang

src/mfast/coder/decoder_v2/fast_decoder_core.h

@@ -107,7 +107,7 @@ template <> class decoder_pmap_saver<pmap_segment_size_zero> {
 template <bool MoreThanOneToken> struct token_base {
   unsigned current_token_;
 
-  void get_token() const { return current_token_; }
+  unsigned get_token() const { return current_token_; }
   void set_token(unsigned token) { current_token_ = token; }
 };