Read a portion from a ringbuffer
[sim, data, NumRead] = ld_read_ringbuf(sim, events, ident_str, datatype, ElementsToRead)
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