rawmidi: do not abort when seeing the hint node

Add the hint node to the nodes that are allowed in rawmidi definitions,
and factor out the detection of such nodes into a common function.

src/rawmidi/rawmidi.c

@@ -987,3 +987,19 @@ ssize_t snd_rawmidi_read(snd_rawmidi_t *rawmidi, void *buffer, size_t size)
 	assert(buffer || size == 0);
 	return (rawmidi->ops->read)(rawmidi, buffer, size);
 }
+
+int snd_rawmidi_conf_generic_id(const char *id)
+{
+	static const char *ids[] = {
+		"comment",
+		"type",
+		"hint",
+	};
+	unsigned int k;
+
+	for (k = 0; k < sizeof ids / sizeof *ids; ++k) {
+		if (strcmp(id, ids[k]) == 0)
+			return 1;
+	}
+	return 0;
+}