core: Remove string.

* string.c (string): Remove.
* module/mes/type-0.mes (string): New function.

module/mes/type-0.mes

@@ -116,3 +116,6 @@
 ;;; core: accessors
 (define (string->list s)
   (core:car s))
+
+(define (string . lst)
+  (make-cell <cell:string> lst 0))

string.c

@@ -18,12 +18,6 @@
  * along with Mes.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-SCM
-string (SCM x) ///((arity . n))
-{
-  return MAKE_STRING (x);
-}
-
 SCM
 string_append (SCM x) ///((arity . n))
 {