fix SFTP download hang

Matt Wixson found and fixed a bug in the SCP/SFTP area where the
code treated a 0 return code from libssh2 to be the same as
EAGAIN while in reality it isn't. The problem caused a hang in
SFTP transfers from a MessageWay server.

CHANGES

@@ -6,6 +6,12 @@
 
                                   Changelog
 
+Daniel Stenberg (1 Apr 2010)
+- Matt Wixson found and fixed a bug in the SCP/SFTP area where the code
+  treated a 0 return code from libssh2 to be the same as EAGAIN while in
+  reality it isn't. The problem caused a hang in SFTP transfers from a
+  MessageWay server.
+
 Daniel Stenberg (28 Mar 2010)
 - Ben Greear: If you pass a URL to pop3 that does not contain a message ID as
   part of the URL, it would previously ask for 'INBOX' which just causes the

RELEASE-NOTES

@@ -44,6 +44,7 @@ This release includes the following bugfixes:
  o multi interface HTTP POST over a proxy using PROXYTUNNEL
  o RTSP GET_PARAMETER
  o timeout after last data chunk was handled
+ o SFTP download hang
 
 This release includes the following known bugs:
 
@@ -57,6 +58,6 @@ advice from friends like these:
  Ryan Chan, Markus Duft, Andrei Benea, Jacob Moshenko, Daniel Johnson,
  Constantine Sapuntzakis, Douglas Steinwand, Thomas Lopatic, Hauke Duden,
  Akos Pasztory, Kenny To, Christopher Conroy, Massimo Callegari,
- Bob Richmond
+ Bob Richmond, Matt Wixson
 
         Thanks! (and sorry if I forgot to mention someone)

lib/sendf.c

@@ -549,7 +549,7 @@ int Curl_read(struct connectdata *conn, /* connection data */
     else if(conn->protocol & PROT_SFTP)
       nread = Curl_sftp_recv(conn, num, buffertofill, bytesfromsocket);
 #ifdef LIBSSH2CHANNEL_EAGAIN
-    if((nread == LIBSSH2CHANNEL_EAGAIN) || (nread == 0))
+    if(nread == LIBSSH2CHANNEL_EAGAIN)
       /* EWOULDBLOCK */
       return -1;
 #endif