Completes the decoder trio. `D3d11vaDecoder::new` had the same cascading unwind as
the VAAPI and Vulkan constructors — four branches each unref'ing the hwdevice by
hand — and `d3d11va_decode_supported` opened a frames context it released on one
exit path while relying on the null check for the other. Both are `AvBuffer` now.
The one surviving `av_buffer_unref` in the file is deliberate: it runs before
ownership is taken, on the `av_hwdevice_ctx_init` failure ahead of `from_raw`.
The Windows gate then caught something worth keeping: `field hw_device is never
read`, in all three decoders. It was true and it was new — the hand-written `Drop`
used to be the field's only reader, so moving the unref into the type left a field
that is *purely* an owner. The compiler cannot express that, so each one now
carries a doc comment saying what it is and an explicit `#[allow(dead_code)]`.
Deleting the field would free the device early; renaming it `_hw_device` would
silence the lint by hiding what it holds. Neither is what we mean.
Verified on BOTH platforms this time. Windows runner .133 (the toolchain env from
the runner notes, plus `PF_FFVK_VULKAN_INCLUDE` for pf-ffvk): `cargo check -p
pf-client-core --all-targets` at EXITCODE=0, clean of the dead-code warnings. Linux
.21: `cargo check --workspace --all-targets` exit 0 / zero errors, pf-client-core
34 passed / 0 failed, pf-encode 33 passed / 0 failed.
enricobuehler
06a406adf2