[Click] hashallocator.cc

[Latency Buster]

On a 64 bit machine:

- size_t shift = sizeof(size_t) * 8 - ffs_msb(_buffer->maxpos + _size);
+  size_t shift = sizeof(size_t) * 8 -
ffs_msb((uint64_t)(_buffer->maxpos + _size));

Thanks,