move strndup back to string.c - used by strdup

src/core/stringextra.c

@@ -271,18 +271,3 @@ void * memscan(const void * addr, int c, size_t size)
   	return (void *) p;
 }
 #endif
-
-char * strndup(const char *s, size_t n)
-{
-	size_t len = strlen(s);
-	char *new;
-
-	if (len>n)
-		len = n;
-	new = malloc(len+1);
-	if (new) {
-		new[len] = '\0';
-		memcpy(new,s,len);
-	}
-	return new;
-}