vlib: use new filename format

vlib/strings/strings.js.v

@@ -0,0 +1,18 @@
+module strings
+
+pub fn repeat(c byte, n int) string {
+	if n <= 0 {
+		return ''
+	}
+	mut arr := [c].repeat(n + 1)
+	arr[n] = `\0`
+	return string(arr,n)
+}
+
+pub fn repeat_string(s string, n int) string {
+/*
+  // TODO: uncomment this. It is commented for now, so that `v doc strings` works
+	res := # s.repeat(n)
+	return res
+*/
+}