Add append_array() method to Array class

(cherry picked from commit 9f23a94b8a)

core/array.h

@@ -64,6 +64,7 @@ public:
 
 	void push_back(const Variant &p_value);
 	_FORCE_INLINE_ void append(const Variant &p_value) { push_back(p_value); } //for python compatibility
+	void append_array(const Array &p_array);
 	Error resize(int p_new_size);
 
 	void insert(int p_pos, const Variant &p_value);