Add missing .gitignore entries

example/.gitignore

@@ -24,6 +24,7 @@ libssh2_config.h
 libssh2_config.h.in
 stamp-h2
 sftp_append
+sftp_write_sliding
 ssh2_echo
 subsystem_netconf
 test-scp
@@ -32,3 +33,4 @@ test-sftp_nonblock
 test-sftp_write
 test-sftp_write_nonblock
 test-ssh2_echo
+x11