Support unescape hexadecimal data encoded in \Xdddd\ escape sequences in HL7 Messages

[gunterze]

package org.dcm4che3.net.hl7;
...
public class UnparsedHL7Message implements Serializable {
...
    /**
     * Return HL7 message with unescaped hexdata from \Xdddd\ escape sequences.
     * Does not unescape \Xdddd\ escape sequences which contains a field separator,
     * component separator, subcomponent separator, repetition separator or escape character. 
     *
     * @return HL7 message with unescaped hexdata from \Xdddd\ escape sequences
     */
    public byte[] unescapeXdddd() { ... }