vlib: use new filename format

vlib/strings/strings.c.v

@@ -0,0 +1,34 @@
+module strings
+
+// strings.repeat - fill a string with `n` repetitions of the character `c`
+pub fn repeat(c byte, n int) string {
+	if n <= 0 {
+		return ''
+	}
+	mut bytes := &byte(0)
+	unsafe { bytes = malloc(n + 1) }
+	C.memset( bytes, c, n )
+	bytes[n] = `0`
+	return string( bytes, n )
+}
+
+// strings.repeat_string - gives you `n` repetitions of the substring `s`
+// NB: strings.repeat, that repeats a single byte, is between 2x
+// and 24x faster than strings.repeat_string called for a 1 char string.
+pub fn repeat_string(s string, n int) string {
+	if n <= 0 || s.len == 0 {
+		return ''
+	}
+	slen := s.len
+	blen := slen*n
+	mut bytes := &byte(0)
+	unsafe { bytes = malloc(blen + 1) }
+	for bi in 0..n {
+		bislen := bi*slen
+		for si in 0..slen {
+			bytes[bislen+si] = s[si]
+		}
+	}
+	bytes[blen] = `0`
+	return string( bytes, blen )
+}