Add a generic bound for u8 and u16 and convert `pred_dc`, `pred_dc_128`,
`pred_dc_left`, `pred_dc_top`, `pred_h`, `pred_v` and `pred_paeth`.

Fixes issue #653.

Josh Holmer authored 6 years ago and Luca Barbato committed 6 years ago

- Rewrite fwd transform functions from C to Rust
- Rewrite 32x32 inv transform functions from C to Rust
- Refactor transform.rs into smaller modules

This commit temporarily removes the calls into the
SIMD optimized functions. These will be rewritten
into Rust and readded in an upcoming PR.

Second part of #650

Solves half #650

The rust compiler DCE works in a different way so conditionals on `cfg!`
should not be used if the code in the branches may not compile.

While at it move the `use` statements where they are needed to avoid
warnings.

Fix #657

Document NASM dependency.

Otherwise cargo-bench would try to call the test runner with --bench and
criterion-only options, making the process fail.

- Don't do duplicate tx_type rdo with bottom-up partition rdo.
- Set tx_type  as DCT_DCT when skip==true during mode decision rdo.
- Add set_tx_size() if rdo_tx_size_type() is not called.

Unbreak encoding without producing the reconstructed video.

* Add code to reorder frames during encoding

* Use BTreeMap instead of VecDequeue to hold input frames

* Implement sign bias in MV prediction

* Disable reuse of learned prob and change ref frame semantics

Use LAST2 instead of ALTREF when the second reference frame is also
in the past

- Move the frame information in a separate struct
- Move the EncoderConfig in api.rs

Manually format parts that skip formatting but don't fix the excess length.

Implement ExactSizeIterator and FusedIterator.

70%-90% faster than before according to criterion.

And use it to compute SAD.

* Format SUBSIZE_LOOKUP slightly then skip it

* Use stable but more verbose way to skip rustfmt

* Fix inter for 12-bit input.

12-bit is a special case that rounds differently.

See 7.11.3.2. Rounding variable derivation process in the spec.

Performs a near-exhaustive-equivalent search of sse-optimum deblocking
level setup at speed <= 3.  Currently always uses SSE, psychovisual
(cdef-dist) comes next.

Above speed 3, levels are set by quantizer.

Rather than converting a level to a threshold decision value and testing values against the threshold,
convert values to levels and compare directly against the filter configuration level.
This will allow binning decisions by level in a radix sort.