Release v1.2.8

Core
 - Release v1.2.8
 - add FreeBSD build support (except test/)
 - add NetBSD/OpenBSD build support (except test/)
Control API
 - control: namehint - do not support 'card' devices
 - control: eld - skip trailing spaces
PCM API
 - pcm: rate: fix the crash for the partial period copy
 - add DragonFlyBSD build support (except test/)
 - pcm: hw_params - copy periods and buffer_time to the local variable
 - pcm: fix the dshare delay reporting
 - pcm: direct plugins: make three more symbols private to library
Use Case Manager API
 - ucm: do not handle multiple Syntax field updates
 - add DragonFlyBSD build support (except test/)
 - add FreeBSD build support (except test/)
 - doc: ucm - more volume notes
 - doc: ucm - add sequence graphs
 - ucm: add NULL check for card_name in open
 - ucm: fix few memory-leaks in the error paths
Async helpers
 - add NetBSD/OpenBSD build support (except test/)
Compatibility routines
 - add NetBSD/OpenBSD build support (except test/)
Configuration
 - Remove non existent SPDIF output on ThinkPad USB-C Dock Gen2
 - add DragonFlyBSD build support (except test/)
 - add NetBSD/OpenBSD build support (except test/)
Documentation
 - doc: ucm - more volume notes
 - doc: ucm - add sequence graphs
Kernel Headers
 - add FreeBSD build support (except test/)
 - add NetBSD/OpenBSD build support (except test/)

Signed-off-by: Jaroslav Kysela <perex@perex.cz>