mie: ctx is now used to query the type of a value

this allows value get_type callbacks to use mie_ctx to obtain mie_type pointers,
rather than having to define their own static versions of the type structs.

mie/arg.c

@@ -18,7 +18,7 @@ struct mie_arg *mie_arg_create(struct mie_type *type)
 	return out;
 }
 
-static struct mie_type *get_type(struct mie_value *v)
+static struct mie_type *get_type(struct mie_value *v, struct mie_ctx *ctx)
 {
 	struct mie_arg *arg = MIE_ARG(v);
 	return arg->arg_type;