message: check TCMALLOC_EXTENSION in pika.cc
diff: #include "pika_define.h"
  #include "pika_slot.h"
  #include "env.h"
  +#ifdef TCMALLOC_EXTENSION
  #include <gperftools/malloc_extension.h>
  +#endif
  PikaConf *g_pika_conf;
  @@ -139,7 +141,9 @@ int main(int argc, char *argv[]) {
  usage();
  exit(-1);
  }
  +#ifdef TCMALLOC_EXTENSION
  MallocExtension::instance()->Initialize();
  +#endif
  PikaConfInit(path);
  rlimit limit;
  