Keep the type of `posarg` consistent

Match the type with the caller and related functions.

mrbgems/mruby-sprintf/src/sprintf.c

@@ -155,17 +155,17 @@ check_next_arg(mrb_state *mrb, int posarg, int nextarg)
 }
 
 static void
-check_pos_arg(mrb_state *mrb, mrb_int posarg, mrb_int n)
+check_pos_arg(mrb_state *mrb, int posarg, mrb_int n)
 {
   if (posarg > 0) {
-    mrb_raisef(mrb, E_ARGUMENT_ERROR, "numbered(%i) after unnumbered(%i)",
+    mrb_raisef(mrb, E_ARGUMENT_ERROR, "numbered(%d) after unnumbered(%d)",
                n, posarg);
   }
   if (posarg == -2) {
-    mrb_raisef(mrb, E_ARGUMENT_ERROR, "numbered(%i) after named", n);
+    mrb_raisef(mrb, E_ARGUMENT_ERROR, "numbered(%d) after named", n);
   }
   if (n < 1) {
-    mrb_raisef(mrb, E_ARGUMENT_ERROR, "invalid index - %i$", n);
+    mrb_raisef(mrb, E_ARGUMENT_ERROR, "invalid index - %d$", n);
   }
 }