bad rwlock

[litlighilit]

• make critical_section and oyobject's readNum, writeLock does nothing if threads:off
• fix the impl that only returns LockError when r&w, (The Reader-Writer Problem). (new module: nimpylib/rwlock)
  may ref:
  • https://nim-lang.github.io/threading/semaphore.html
  • man 3p pthread_rwlock_trywrlock (pthread.h)

ref:
https://github.com/nimpylib/npython/blob/master/Include%2Fcpython%2Fcritical_section.nim