Merge commit '81a4cb8e'

* commit '81a4cb8e':
  vf_hwmap: Add reverse mapping for hardware frames
  vf_hwmap: Add device derivation
  hwcontext: Improve allocation in derived contexts
  hwcontext_qsv: Implement mapping frames to the child device type
  hwcontext_qsv: Implement mapping frames from the child device type
  hwcontext: Add frame context mapping for nontrivial contexts
  hwcontext_qsv: Support derivation from child devices
  avconv: Support setting the hardware device to use when filtering
  avconv_hw: Add implicit device creation with default parameters
  vp9_raw_reorder_bsf: Remove a redundant allocation

This commit is a noop, see
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d81be0a6Merged-by: James Almer <jamrial@gmail.com>