Writes HL7 messages to an OutputStream. The character set defaults to US-ASCII. It can be changed by setting the system property ca.uhn.hl7v2.llp.charset to another value that is the name of a valid java.nio.charset.Charset. If this property is set to "default", then the system default is used.
@author Damian Horton; mods by Bryan Tripp
@author Christian Ohr