- Clarified contract of IAnnotationMap.getLockObject() and
setLockObject().
- Clarified contract of AnnotationModel.getLockObject() and
setLockObject().
- Added warning in AnnotationMap.setLockObject() if the lock is changed
- Removed dead code in AnnotationModel.cleanup because mapLock can't be
null.

Co-authored-by: Andrey Loskutov <loskutov@gmx.de>