Merge pull request #1098 from monaka/pr-fix-type-in-dump.h

Fix a type mismatch.

include/mruby/dump.h

@@ -18,7 +18,7 @@ int mrb_dump_irep_binary(mrb_state*, size_t, int, FILE*);
 int mrb_dump_irep_cfunc(mrb_state *mrb, size_t n, int, FILE *f, const char *initname);
 int32_t mrb_read_irep_file(mrb_state*, FILE*);
 #endif
-int mrb_read_irep(mrb_state*, const uint8_t*);
+int32_t mrb_read_irep(mrb_state*, const uint8_t*);
 
 #ifdef ENABLE_STDIO
 mrb_value mrb_load_irep_file(mrb_state*,FILE*);