Make documentation for `mosquitto_pub -l` match reality

Blank lines are sent as empty messages.

Closes #1474. Thanks to majekw.

ChangeLog.txt

@@ -26,6 +26,8 @@ Clients:
 - Fix `mosquitto_pub -l` hang when stdin stream ends. Closes #1448.
 - Fix `mosquitto_pub -l` not sending the final line of stdin if it does not
   end with a new line. Closes #1473.
+- Make documentation for `mosquitto_pub -l` match reality - blank lines are
+  sent as empty messages. Closes #1474.
 
 Build:
 - Added `CLIENT_STATIC_LDADD` to makefile builds to allow more libraries to be

man/mosquitto_pub.1.xml

@@ -338,7 +338,7 @@
 				<term><option>-l</option></term>
 				<term><option>--stdin-line</option></term>
 				<listitem>
-					<para>Send messages read from stdin, splitting separate lines into separate messages. Note that blank lines won't be sent.</para>
+					<para>Send messages read from stdin, splitting separate lines into separate messages.</para>
 				</listitem>
 			</varlistentry>
 			<varlistentry>