Description:
------------
php_ssh2_sftp_stream_read() doesn't check for the End OF File condition.
So, feof() on such streams always returns false.

Also negative return values from libssh2_sftp_read aren't handled, correctly.

I have attached a patch which fixes these problems in php_ssh2_sftp_stream_read (and php_ssh2_sftp_stream_write, which has similar problems)

Reproduce code:
---------------
Example:

<?php

// create sftp ressource $sftp

$h = fopen("ssh2.sftp://$sftp/tmp/testfile", 'r');

while (!feof($h)) {
    echo(fread($h,10));
}
?>

Here is the patch:
 
Index: ssh2_sftp.c
===================================================================
--- ssh2_sftp.c	(Revision 297176)
+++ ssh2_sftp.c	(Arbeitskopie)
@@ -107,8 +107,11 @@
 static size_t php_ssh2_sftp_stream_write(php_stream *stream, const char *buf, size_t count TSRMLS_DC)
 {
 	php_ssh2_sftp_handle_data *data = (php_ssh2_sftp_handle_data*)stream->abstract;
+	ssize_t bytes_written;
 
-	return libssh2_sftp_write(data->handle, buf, count);
+	bytes_written = libssh2_sftp_write(data->handle, buf, count);
+
+	return (size_t)(bytes_written<0 ? 0 : bytes_written);
 }
 /* }}} */
 
@@ -117,8 +120,13 @@
 static size_t php_ssh2_sftp_stream_read(php_stream *stream, char *buf, size_t count TSRMLS_DC)
 {
 	php_ssh2_sftp_handle_data *data = (php_ssh2_sftp_handle_data*)stream->abstract;
+	ssize_t bytes_read;
 
-	return libssh2_sftp_read(data->handle, buf, count);
+	bytes_read = libssh2_sftp_read(data->handle, buf, count);
+
+	stream->eof = (bytes_read <= 0 && bytes_read != LIBSSH2_ERROR_EAGAIN);
+
+	return (size_t)(bytes_read<0 ? 0 : bytes_read);
 }
 /* }}} */
 


Expected result:
----------------
The example outputs the file and ends.

Actual result:
--------------
Without the patch, the loop runs forever.