Update ModbusMaster.h
Update ModbusMaster.h

Changed response timeout type to 16-bit unsigned.

Changed response timeout to 2000 milliseconds.
4-20ma/ModbusMaster,kintel/ModbusMaster,kintel/ModbusMaster,kintel/ModbusMaster,4-20ma/ModbusMaster,4-20ma/ModbusMaster,kintel/ModbusMaster