[vlc-devel] Backport OS/2 condition variable improvement to vlc 2.2

[KO Myung-Hun]

Hi/2.

This fixes the problem that CPU load peaks to 99.9% when playing
youtube live streaming.

[PATCH 1/4] os2: thread: implement vlc_cond_signal() correctly
[PATCH 2/4] src: os2: fix locking at quit
[PATCH 3/4] os2: thread: use sys/builtin.h instead of 386/builtin.h
[PATCH 4/4] os2: thread: determine cancelable state with killable