cgen: fix arr.insert(0, [1,2,3]) and arr.prepend([1,2,3])

vlib/builtin/array_test.v

@@ -134,6 +134,15 @@ fn test_insert() {
 	assert b[0] == f64(1.1)
 }
 
+fn test_insert_many() {
+	mut a := [3, 4]
+	a.insert(0, [1, 2])
+	assert a == [1,2,3,4]
+	b := [5,6]
+	a.insert(1, b)
+	assert a == [1,5,6,2,3,4]
+}
+
 fn test_prepend() {
 	mut a := []int{}
 	assert a.len == 0
@@ -147,6 +156,15 @@ fn test_prepend() {
 	assert b[0] == f64(1.1)
 }
 
+fn test_prepend_many() {
+	mut a := [3,4]
+	a.prepend([1,2])
+	assert a == [1,2,3,4]
+	b := [5,6]
+	a.prepend(b)
+	assert a == [5,6,1,2,3,4]
+}
+
 fn test_strings() {
 	a := ['a', 'b', 'c']
 	assert a.str() == "['a', 'b', 'c']"
@@ -166,7 +184,6 @@ fn test_compare_ints() {
 }
 */
 
-
 fn test_repeat() {
 	{
 		a := [0].repeat(5)