Read a portion from a ringbuffer relative to the currently set marker position
[sim, data] = ld_relread_ringbuf(sim, events, ident_str, datatype, ElementsToRead, relPos)
data *+(ElementsToRead) - data
ident_str (string) - name of the ringbuffer
datatype - ORTD datatype of the ringbuffer (for now only ORTD.DATATYPE_FLOAT)
ElementsToRead (integer) - number of elements to read from the ringbuffer
relPos - UINT - position relative to the currently set marker to start reading from