Merge branch 'dev-kubat' into 'master'

inc/lektor/cmd.h

inc/lektor/thread.h

inc/mthread/mthread.h

inc/mthread/mthread_internal.h

meson.build

meson_options.txt

src/cmd.c

src/database/playlist.c

src/database/queue.c

src/main/lkt.c

src/main/server.c

src/mthread.c

src/mthread/mthread_cond.c

src/mthread/mthread_key.c

src/mthread/mthread_mutex.c

src/mthread/mthread_once.c

src/mthread/mthread_sem.c

src/mthread/mthread_tst.c

src/uri.c