riched20: Flush the clipboard before exiting the test.

dlls/riched20/tests/Makefile.in

@@ -3,7 +3,7 @@ TOPOBJDIR = ../../..
 SRCDIR    = @srcdir@
 VPATH     = @srcdir@
 TESTDLL   = riched20.dll
-IMPORTS   = riched20 user32 gdi32 kernel32
+IMPORTS   = riched20 ole32 user32 gdi32 kernel32
 
 CTESTS = \
 	editor.c

dlls/riched20/tests/editor.c

@@ -1411,5 +1411,6 @@ START_TEST( editor )
     }
   }
 
+  OleFlushClipboard();
   ok(FreeLibrary(hmoduleRichEdit) != 0, "error: %d\n", (int) GetLastError());
 }