The IO Ring now supports bashing multiple submissions and can handle
multiple files at the same time.
Hashing small files using XXH3_128bits() instead of the streaming
pipeline(XXH3_128bits_reset(), XXH3_128bits_update(),
XXH3_128bits_digest()), this reduses the overhead of creating a state
and digest, coupled with the IO Ring it improves the hashing of small
files whose size is inferior to the size of IO Ring buffers
This dispatcher can not be added in a unity build and we must remove
AVX2 or AVX512 compilation flags, link xxh_x86dispatch.c in the
compilation command. The compilaiton throws two warnings about function
with internal linkage but not defined, they are defined in
xxh_x86dispatch.c so it's harmless warnings
Making the MPMC queue support when producers are consumers at the same
time by adding a variable work, mpmc_push_work() that increments work
and mpmc_task_done() that decrements work, and if work = 0 calls
mpmc_producers_finished() that pushes poinsons to wake up sleeping
threads and make them return NULL
Replacing DirQueue, a queue growable with realloc with the MPMC queue
Instead of writing directly to file_hashes.txt, hash_workers now are
using a local arena, writing everything once at the end
using #pragma once to ensure that a given header file is included only
once in a single compilation unit
