Fix forward class declaration.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

kdirstat/kstdcleanup.h

@@ -18,11 +18,13 @@
 
 // Forward declarations
 class TDEActionCollection;
-class KDirStat::KCleanup;
 
 
 namespace KDirStat
 {
+    // Forward declarations
+    class KCleanup;
+
     /**
      * Predefined standard @ref KCleanup actions to be performed on
      * @ref KDirTree items.