Added uiParentDestroy(). Now to implement.

docs/uiParent.md

@@ -10,7 +10,10 @@ void *Internal;
 This pointer is used internally by libui. Do not attempt to alter it or access/alter its data.
 
 ## func Destroy()
-TODO
+```c
+void uiParentDestroy(uiParent *p);
+```
+Destroys the uiParent. This also destroys the main child, if any. This is called by `uiWindowDestroy()` and uiTab's/uiGroup's `uiControlDestroy()`.
 
 ## func Handle()
 ```c

ui.idl

@@ -59,7 +59,7 @@ interface Control {
 
 interface Parent {
 	field Internal *void;
-	// TODO destroy
+	func Destroy(void);
 	// TODO object destruction debug handler
 	func Handle(void) uintptr_t;
 	func SetMainControl(c *Control);