HEVC: Fixes for SEI handling in bitstream and CodecPrivate

Fixes #1076,
tests: include test result for case 442 added in 8d32a62
HEVC: Write CodecPrivate::configuration_version = 1
HEVC: add test case for keeping user data

See #1076.
HEVC: Detect IDR_N_LP as keyframes
ChangeLog: update