Added sftp definition file, updated libssh2 definition file, updated setup.py. Added SFTP and listener extension classes and methods. Added direct tcp methods to session. Updated read from channel code to be more efficient

Author: Pan

MANIFEST.in

@@ -26,6 +26,7 @@
               sources=sources,
               libraries=['ssh2'],
               # extra_compile_args=["-O3"],
+              extra_compile_args=["-ggdb"],
           ),
 ]