Update memory.d

@wilzbach: I've updated the documentation to reuse the semantics of `destroy`. This simplifies and modularizes matters a great deal.

Author: andralex

src/core/memory.d

@@ -939,28 +939,24 @@ Note: Users should prefer $(REF destroy, object)` to explicitly finalize objects
 and only resort to $(REF __delete, core,memory) when $(REF destroy, object)
 would not be a feasible option.
 
-In detail, `__delete` does the following:
+In detail, `__delete(x)` returns with no effect if `x` is `null`. Otherwise, it
+performs the following actions in sequence:
 $(UL
-
-    $(LI If `t` is a class object reference, and
-        there is a destructor for that class, the destructor
-        is called for that object instance.
-    )
-    $(LI Otherwise, the garbage collector is called to immediately free the
-        memory allocated for the class instance or struct instance.
-        If the garbage collector was not used to allocate the memory for
-        the instance, undefined behavior will result.
+    $(LI
+        Calls `.object.destroy(*x)` (if `x` is a pointer) or `.object.destroy(x)`
+        (otherwise) to destroy the referred entity.
     )
-    $(LI If `t` is a pointer or a dynamic array,
-        the garbage collector is called to immediately release the
-        memory.
-        If the garbage collector was not used to allocate the memory for
-        the instance, undefined behavior will result.
+    $(LI
+        Frees the memory allocated for `x`. If `x` is a reference to a class
+        or interface, the memory allocated for the underlying instance is freed. If `x` is
+        a pointer, the memory allocated for the pointed-to object is freed. If `x` is a
+        built-in array or associative array, the memory allocated for the array is freed.
+        If `x` does not refer to memory previously allocated with `new` (or the lower-level
+        equivalents in the GC API), the behavior is undefined.
     )
-    $(LI The pointer, dynamic array, or reference is set to `null`
-        after the delete is performed.
-        Any attempt to reference the data after the deletion via another
-        reference to it will result in undefined behavior.
+    $(LI
+        Lastly, `x` is set to `null`. Any attempt to read or write the freed memory via
+        other references will result in undefined behavior.
     )
 )