added three more public functions I found lacking man pages

docs/libssh2_channel_receive_window_adjust.3

@@ -0,0 +1,28 @@
+.\" $Id: libssh2_channel_receive_window_adjust.3,v 1.1 2009/03/15 22:59:46 bagder Exp $
+.\"
+.TH libssh2_channel_receive_window_adjust 3 "15 Mar 2009" "libssh2 0.15" "libssh2 manual"
+.SH NAME
+libssh2_channel_receive_window_adjust - adjust the channel window
+.SH SYNOPSIS
+#include <libssh2.h>
+
+unsigned long
+libssh2_channel_receive_window_adjust(LIBSSH2_CHANNEL * channel,
+                                      unsigned long adjustment,
+                                      unsigned char force);
+
+.SH DESCRIPTION
+Adjust the receive window for a channel by adjustment bytes. If the amount to
+be adjusted is less than LIBSSH2_CHANNEL_MINADJUST and force is 0 the
+adjustment amount will be queued for a later packet.
+.SH RETURN VALUE
+Returns the new size of the receive window (as understood by remote end). Note
+that the window value sent over the wire is strictly 32bit, but this API is
+made to return a 'long' which may not be 32 bit on all platforms.
+.SH ERRORS
+In 1.0 and earlier, this function returns LIBSSH2_ERROR_EAGAIN for
+non-blocking channels where it would otherwise block. However, that is a
+negative number and this function only returns an unsigned value and this then
+leads to a very strange value being returned.
+.SH SEE ALSO
+libssh2_channel_window_read_ex(3)