Fix printf format for size_t and mb_size_t

diff --cc src/store_client.cc
index bf87633ba4505c4fe3b6164df0022d1a47bc7331,bf87633ba4505c4fe3b6164df0022d1a47bc7331..4da1d4c7ab0bd9d3defbfd8792874e346fad892f
--- 1/src/store_client.cc
--- 2/src/store_client.cc
+++ b/src/store_client.cc
@@@ -857,7 -857,7 +857,7 @@@ store_client::dumpStats(MemBuf * output
  
      output->appendf("\tClient #%d, %p\n", clientNumber, _callback.callback_data);
      output->appendf("\t\tcopy_offset: %" PRId64 "\n", copyInto.offset);
--    output->appendf("\t\tcopy_size: %d\n", copyInto.length);
++    output->appendf("\t\tcopy_size: %" PRIuSIZE "\n", copyInto.length);
      output->append("\t\tflags:", 8);
  
      if (flags.disk_io_pending)