Update all new Tasks

Task/String-matching/OCaml/string-matching-5.ocaml

@@ -0,0 +1,12 @@
+let match2_num s1 s2 =
+  let len1 = String.length s1
+  and len2 = String.length s2 in
+  if len1 < len2 then (false, 0) else
+    let rec aux i n =
+      if i < 0 then (n <> 0, n) else
+        let sub = String.sub s1 i len2 in
+        if (sub = s2)
+        then aux (pred i) (succ n)
+        else aux (pred i) (n)
+    in
+    aux (len1 - len2) 0