Add notre regarding OutbufHighwaterMark=0 for Linux and BSD to allow

auto-tuning based on the negotiated MSS (3.13b and higher only).

ctrl/sbbs.ini

@@ -62,6 +62,11 @@
 ; At what size to send the current output buffer regardless of timeout
 ; ie: Send output whenever there are at least this many bytes waiting.
 ; This should definately not be higher than the MTU.
+;
+; On Linux and BSD (Any platform which supports the TCP_MAXSEG socket opt)
+; This can (and probably should) be set to zero to automagically set the
+; highwater mark to the MSS and ensure no single call to send() is larger
+; than this.
         OutbufHighwaterMark=1024
 ; Timout to wait for output buffer to fill (Milliseconds)
 ; If there is ANY data in the output buffer after waiting this long, send