PR705rawspd - Takes an spd measurement and returns the results.
rawspd = PR705rawspd(timeout)
timeout (scalar) - Timeout period in seconds.
rawspd (1xN char) - The raw character array resulting from a measurement.
This will be an empty string if the timeout period was reached.
errcode (scalar) - The error code reported by the meter (success = 0).
12/06/12 zlb Wrote it.