Allow workspace contents to be moved if there are only floating children

include/con.h

@@ -39,6 +39,12 @@ bool con_is_leaf(Con *con);
  */
 bool con_is_split(Con *con);
 
+/**
+ * Returns true if this node has regular or floating children.
+ *
+ */
+bool con_has_children(Con *con);
+
 /**
  * Returns true if this node accepts a window (if the node swallows windows,
  * it might already have swallowed enough and cannot hold any more).