clang: suppress a warning
clang: suppress a warning

Add missing cast.

    lib/token.c:61:19: warning: assigning to 'byte *'
          (aka 'unsigned char *') from 'char *' converts between pointers to integer
          types with different sign [-Wpointer-sign]
      tokenizer->curr = GRN_TEXT_VALUE(str);
                      ^ ~~~~~~~~~~~~~~~~~~~

komainu8/groonga,komainu8/groonga,cosmo0920/groonga,hiroyuki-sato/groonga,myokoym/groonga,hiroyuki-sato/groonga,kenhys/groonga,hiroyuki-sato/groonga,kenhys/groonga,komainu8/groonga,hiroyuki-sato/groonga,myokoym/groonga,cosmo0920/groonga,redfigure/groonga,groonga/groonga,myokoym/groonga,groonga/groonga,kenhys/groonga,komainu8/groonga,cosmo0920/groonga,kenhys/groonga,redfigure/groonga,redfigure/groonga,groonga/groonga,groonga/groonga,naoa/groonga,naoa/groonga,hiroyuki-sato/groonga,naoa/groonga,myokoym/groonga,kenhys/groonga,redfigure/groonga,kenhys/groonga,groonga/groonga,groonga/groonga,naoa/groonga,cosmo0920/groonga,naoa/groonga,naoa/groonga,cosmo0920/groonga,cosmo0920/groonga,groonga/groonga,komainu8/groonga,cosmo0920/groonga,myokoym/groonga,kenhys/groonga,komainu8/groonga,cosmo0920/groonga,redfigure/groonga,myokoym/groonga,redfigure/groonga,komainu8/groonga,komainu8/groonga,hiroyuki-sato/groonga,redfigure/groonga,myokoym/groonga,kenhys/groonga,groonga/groonga,naoa/groonga,redfigure/groonga,myokoym/groonga,hiroyuki-sato/groonga,naoa/groonga,hiroyuki-sato/groonga