Add missing ClientFormatListResponse() call in RDP plugin clipboard, …
…fixes #809 (closed) @antenore @Nastasi: I need a bit of regression testing on this PR, which fixes malfuncioning clipboard from XP server to remmina. If you can, test the clipboard with other different os. This patch could also fix some other clipboard issues (i.e. #916 (closed), #900 (closed)...), we need to take a look at those issues.