Merge tag 'v1.10.0'

Release v1.10.0 Ruddy Duck

2021-03-09 v1.10.0 "Ruddy Duck"

  This maintenance release adds support for darwin20 and new codec controls, as
  well as numerous bug fixes.

  - Upgrading:

    New codec control is added to disable loopfilter for VP9.

    New encoder control is added to disable feature to increase Q on overshoot
    detection for CBR.

    Configure support for darwin20 is added.

    New codec control is added for VP9 rate control. The control ID of this
    interface is VP9E_SET_EXTERNAL_RATE_CONTROL. To make VP9 use a customized
    external rate control model, users will have to implement each callback
    function in vpx_rc_funcs_t and register them using libvpx API
    vpx_codec_control_() with the control ID.

  - Enhancement:

    Use -std=gnu++11 instead of -std=c++11 for c++ files.

  - Bug fixes:

    Override assembler with --as option of configure for MSVS.

    Fix several compilation issues with gcc 4.8.5.

    Fix to resetting rate control for temporal layers.

    Fix to the rate control stats of SVC example encoder when number of spatial
    layers is 1.

    Fix to reusing motion vectors from the base spatial layer in SVC.

    2 pass related flags removed from SVC example encoder.

Bug: webm:1712

Change-Id: I4d807da7aee5a4d9d7a7af66b927983622e9cefa