ppsi for wrs requres locks in shmem when shmem is changing. Since servo is
shared between wrs and wrpc fixes had to be implemented.
Since there is no shmem in wrpc, dummy function for locking had to be added.
As a side effect include/libwr/shmem.h was added.
Signed-off-by: Adam Wujek <adam.wujek@cern.ch>