[v3] os: unexport LockServer() and UnlockServer() from public module API
These functions work on server process level, and shouldn't be touched by drivers at all, thus shouldn't be exported to them.
Changes v3:
- resolved conflicts
- squashed adding serverlock.h and moving it to os/ dir into one commit
Changes v2:
- move definition of LOCK_SERVER into meson
- make LockServerUseMsg() a real function instead of inline
Edited by Enrico Weigelt, metux IT consult .