libssh2 1.4.1

This release includes the following bugfixes:

 o build error with gcrypt backend
 o always do "forced" window updates to avoid corner case stalls
 o aes: the init function fails when OpenSSL has AES support
 o transport_send: Finish in-progress key exchange before sending data
 o channel_write: acknowledge transport errors
 o examples/x11.c: Make sure sizeof passed to read operation is correct
 o examples/x11.c:,Fix suspicious sizeof usage
 o sftp_packet_add: verify the packet before accepting it
 o SFTP: preserve the original error code more
 o sftp_packet_read: adjust window size as necessary
 o Use safer snprintf rather then sprintf in several places
 o Define and use LIBSSH2_INVALID_SOCKET instead of INVALID_SOCKET
 o sftp_write: cannot return acked data *and* EAGAIN
 o sftp_read: avoid data *and* EAGAIN
 o libssh2.h: Add missing prototype for libssh2_session_banner_set()

This release would not have looked like this without help, code, reports and
advice from friends like these:

 Armen Babakhanian, Paul Howarth, Matthew Booth, Steven Dake, Peter Stuge,
 Matt Lawson, Tom Weber, Alexander Lamaison
 
        Thanks! (and sorry if I forgot to mention someone)