Function remove

src/common/classes/alloc.cpp:222–233

	template <class T>
	void remove(T* e)
	{
		fb_assert(e);
		fb_assert(e->prev);

		// adjust previous pointer in next element ...
		if (e->next)
			e->next->prev = e->prev;

		// ... and next pointer in previous element
		*(e->prev) = e->next;
	}

	template <class T>
	T* pop(T* e)