Avoid unnecessary string duplication

Long description:

This patch removes an unnecessary string duplication that was only
used to avoid a compiler warning.

To apply this patch, use:
curl http://cr.i3wm.org/patch/470/raw.patch | git am

@@ -104,8 +104,8 @@ static int parse_align(cfg_t *context, cfg_opt_t *option, const char *value, voi

                 die("Invalid alignment attribute found in section %s, line %d: \"%s\"\n"

                     "Valid attributes are: left, center, right\n", context->name, context->line, value);

-        char **cresult = result;

-        *cresult = sstrdup(value);

+        const char **cresult = result;

+        *cresult = value;

         return 0;

 }