- Add -K keepalive flag for dropbear and dbclient

- Try to reduce the frequency of select() timeouts
- Add a max receive window size of 1MB

--HG--
extra : convert_revision : 9aa22036cb511cddb35fbc0e09ad05acb39b64d1

dbclient.1

@@ -79,6 +79,13 @@ connection will abort as normal.
 Specify the per-channel receive window buffer size. Increasing this 
 may improve network performance at the expense of memory use. Use -h to see the
 default buffer size.
+.TP
+.B \-K \fItimeout_seconds
+Ensure that traffic is transmitted at a certain interval in seconds. This is
+useful for working around firewalls or routers that drop connections after
+a certain period of inactivity. The trade-off is that a session may be
+closed if there is a temporary lapse of network connectivity. A setting
+if 0 disables keepalives.
 .SH AUTHOR
 Matt Johnston (matt@ucc.asn.au).
 .br