add some .o files to gitignore

.gitignore

@@ -1,3 +1,6 @@
 doble_initial.exe
 *.o
 *.exe
+runTests
+stack.o
+test_stack.o

bintree.c

@@ -26,7 +26,18 @@ void *nextTreeData(TreeNode *root)
 // Releases all memory resources (including data copies).
 void clearTree(TreeNode *root)
 {
-
+    if(root->right)
+        clearTree(root->right);
+    else if (root->left)
+        clearTree(root->left);
+    else
+    {
+        root->data = 0;
+        free(root->data);
+        free(root->right);
+        free(root->left);
+        free(root);
+    } 
 }
 
 // Returns the number of entries in the tree given by root.