AuxiliaryTypeProperty syntax

[podborski]

In HEIF we have this definition:

aligned(8) class AuxiliaryTypeProperty
extends ItemFullProperty('auxC', version = 0, flags) {
	string aux_type;
	template unsigned int(8) aux_subtype[];
		// until the end of the box, the semantics depend on the aux_type value
}

Here the template keyword is not needed as there is no default value specified (see ISOBMFF spec).
Also do we define the string anywhere? I could not find it.

[cconcolato]

We define utf8string and utfstring (for UTF-8 or 16) but not string