libaom v3.8.1 release candidate 1

[Wan-Teh Chang]

Hi everyone,

libaom v3.8.1 release candidate 1 is available. The release tag is
v3.8.1-rc1. Your testing will be greatly appreciated.

This release includes several bug fixes. This release is ABI
compatible with the last release. See
https://aomedia.googlesource.com/aom/+log/v3.8.0..v3.8.1-rc1 for all the
commits in this release.

- Bug Fixes
* aomedia:3520: get_cubic_kernel_dbl: Assertion `0 <= x && x < 1'
failed.
* aomedia:3526: alloc_compressor_data() is called during every
aom_codec_control() call on the encoder.
* aomedia:3527: aom/av1/encoder/mcomp.c:1810: av1_full_pixel_search:
Assertion `ms_params->ms_buffers.ref->width ==
ms_params->ms_buffers.src->width' failed.
* aomedia:3534: libaom encoder crashed by AOM_USAGE_ALL_INTRA and
AOM_EFLAG_NO_REF_LAST flags.
* b:310455204: Recreate workers if necessary.
* b:310548198: Update frame size in actual encoding.
* b:314858909: Do not use adaptive error estimate.
* Fix a hang of cmake on arm64 macOS with cmake 3.27.0 or later.

Thanks,
Wan-Teh Chang