Add option WITH_DEBUG_RINGBUFFER to enable/disable ringbuffer debugging
at compile time.
Even if it is possible to filter specific wlog tags it's not yet
possible to exclude one or more and ringbuffer adds massive debugging
output if enabled and WLOG_LEVEL is set to DEBUG.
This adds a ringbuffer implementation that targets bytes sending.
The ringbuffer can grow when there's not enough room, that's why it's
not thread-safe (locking must be done externally). It will be shrinked
to its initial size as soon as the used bytes are the half of the
initial size.
