freestanding: malloc/free with mm_alloc an mm_free

Added more array support that depends on malloc. Added string clone (that uses malloc). Added test for it. Eliminated stack allocated buffers from most of the unit checks.

vlib/builtin/bare/array_bare.v

@@ -34,3 +34,21 @@ fn (a mut array) set(i int, val voidptr) {
 	}
 	mem_copy(a.data + a.element_size * i, val, a.element_size)
 }
+
+
+// array.repeat returns new array with the given array elements
+// repeated `nr_repeat` times
+pub fn (a array) repeat(nr_repeats int) array {
+	assert nr_repeats >= 0
+
+	arr := array {
+		len: nr_repeats * a.len
+		cap: nr_repeats * a.len
+		element_size: a.element_size
+		data: malloc(nr_repeats * a.len * a.element_size)
+	}
+	for i := 0; i < nr_repeats; i++ {
+		mem_copy(arr.data + i * a.len * a.element_size, a.data, a.len * a.element_size)
+	}
+	return arr
+}