Make the type of the read/write lock of AIThreadSafe a template parameter.

This allows passing a different type than the default AIRWLock for
debugging purposes.

The signature of the class used for RWLOCK should be:

struct RWLock {
  // Default constructor.
  RWLock(void);

  // Block until it's safe to read the data.
  // high_priority is a hint that granting this thread the read lock is more important than granting another thread a write lock.
  void rdlock(bool high_priority = false);
  // Release the obtained read lock.
  void rdunlock();
  // Block until it's safe to write to the data.
  void wrlock();
  // Release the obtained write lock.
  void wrunlock();
  // Convert the obtained write lock into a read lock.
  void wr2rdlock();
  // Block until it is possible to convert the obtained read lock into a write lock.
  void rd2wrlock();

  // Return true when a read or write is obtained and subsequent calls to release the lock are expected.
  bool isLocked() const;
};
Add AINRLock for debugging purposes.

This class can be used as RWLOCK parameter to AIThreadSafe to check that
data is only accessed by a single thread (like
AIThreadSafeSingleThreaded) AND is never write locked when a read or
write lock was already obtained (by the same thread). It doesn't
actually lock anything, it just keeps track if the "lock" was obtained
before. The use case is to check if STL containers aren't being used
(read or write locked) by a calling function when additional write
access is necessary, as write access might invalidate iterator that
point to the container (where the previous lock was taken).
Remove unused variable.
Use viewList_t and child_list_t in appropriate places.

Both types are currently the same, but soon they will be made different.
Currently they are used a bit mixed up. This patch fixes that.