Define ~DirManager, to avoid GCC warning:

`class rfb::win32::FolderManager' has virtual functions but non-virtual destructor



git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@3362 3789f03b-4d11-0410-bbf8-ca57d06f2519
diff --git a/common/rfb/DirManager.h b/common/rfb/DirManager.h
index cfa07b5..9dd848c 100644
--- a/common/rfb/DirManager.h
+++ b/common/rfb/DirManager.h
@@ -31,6 +31,7 @@
 namespace rfb {
   class DirManager {
   public:
+    virtual ~DirManager() {};
     virtual bool createDir(char *pFullPath) = 0;
     virtual bool renameIt(char *pOldName, char *pNewName) = 0;
     virtual bool deleteIt(char *pFullPath) = 0;