Fixes#3211.
Adds the `--[no-]pass-through` flag which enables/disables pass-through mode.
* `zstdcat`, `zcat`, and `gzcat` default to `--pass-through`.
Pass-through mode can be disabled by passing `--no-pass-through`.
* All other binaries default to not setting pass-through mode.
However, we preserve the legacy behavior of enabling pass-through
mode when writing to stdout with `-f` set, unless pass-through
mode is explicitly disabled with `--no-pass-through`.
Adds a new test for this behavior that should codify the behavior we want.
fileio_types.h cannot be parsed by itself
because it relies on basic types defined in `lib/common/mem.h`.
As for #3231, it likely wasn't detected because `mem.h` was probably included before within target files.
But this is not proper.
A "easy" solution would be to add the missing include,
but each dependency should be considered "bad" by default,
and only allowed if it brings some tangible value.
In this case, since these types are only used to declare internal structure variables
which are effectively only flags,
I believe it's really not valuable to add a dependency on `mem.h` for this purpose
while the standard `int` type can do the same job.
I was expecting some compiler warnings following this change,
but it turns out we don't use `-Wconversion` by default on `zstd` source code,
so there is none.
Nevertheless, I enabled `-Wconversion` locally and proceeded to fix a few conversion warnings in the process.
Adding `-Wconversion` to the list of flags used for `zstd` is something I would be favorable over the long term,
but it cannot be done overnight,
because the nb of places where this warning is triggered is daunting.
Better progressively reduce the nb of triggered `-Wconversion` warnings before enabling this flag by default.
* Refactored fileio.c:
- Extracted asyncio code to fileio_asyncio.c/.h
- Moved type definitions to fileio_types.h
- Moved common macro definitions needed by both fileio.c and fileio_asyncio.c to fileio_common.h
* Bugfix - rename fileio_asycio to fileio_asyncio
* Added copyrights & license to new files
* CR fixes
