Ring Buffer Improvement

[tfjmp]

Add:

• Log if we overwrite.
• Means to have some information about the state of the buffers.

[dme26]

Noting also that it might potentially be useful to be able to check the state-of-buffer information from user-space, e.g., to determine whether records are likely to have been flushed or not (e.g., if the ring buffers are empty).

[tfjmp]

As of this commit: 27e5158

Can check from userspace how many graph elements have been dropped.

May look next as how to know how full the queue currently is.