Method resize

fdbclient/include/fdbclient/VersionedMap.h:113–116

	PTree<T> const* operator[](size_t i) const { return entries_[i]; }

	void resize(size_t sz) {
		size_ = sz;
		ASSERT(size_ < N);
	}

	void push_back(PTree<T> const* node) {
		entries_[size_++] = { node };