ta: remove ta_find_parent()

Some mpv code once needed this, but it was removed in 2015.

ta/ta.c

@@ -291,22 +291,6 @@ bool ta_set_destructor(void *ptr, void (*destructor)(void *))
     return true;
 }
 
-/* Return the ptr's parent allocation, or NULL if there isn't any.
- *
- * Warning: this has O(N) runtime complexity with N sibling allocations!
- */
-void *ta_find_parent(void *ptr)
-{
-    struct ta_header *h = get_header(ptr);
-    if (!h || !h->next)
-        return NULL;
-    for (struct ta_header *cur = h->next; cur != h; cur = cur->next) {
-        if (cur->size == CHILDREN_SENTINEL)
-            return PTR_FROM_HEADER(cur->ext->header);
-    }
-    return NULL;
-}
-
 #ifdef TA_MEMORY_DEBUGGING
 
 #include <pthread.h>

ta/ta.h

@@ -52,7 +52,6 @@ void ta_free(void *ptr);
 void ta_free_children(void *ptr);
 bool ta_set_destructor(void *ptr, void (*destructor)(void *));
 bool ta_set_parent(void *ptr, void *ta_parent);
-void *ta_find_parent(void *ptr);
 
 // Utility functions
 size_t ta_calc_array_size(size_t element_size, size_t count);

ta/ta_talloc.h

@@ -38,7 +38,6 @@
 #define talloc_realloc_size             ta_xrealloc_size
 #define talloc_new                      ta_xnew_context
 #define talloc_set_destructor           ta_xset_destructor
-#define talloc_parent                   ta_find_parent
 #define talloc_enable_leak_report       ta_enable_leak_report
 #define talloc_size                     ta_xalloc_size
 #define talloc_zero_size                ta_xzalloc_size