References for existing structures

[tomaskender]

This new feature allows users to define attributes that reference an existing structure.

Use case:

Person - name <string>
       - partner <Person>
       - children <Person[]>
 
 person.parents[0].parents[0].name

Changes had to be made to _addStruct and other parts of modules.cpp. The most serious one was the predeclaration of a struct symbol in it's parent object. It's assigned as an attribute of it's parent before attributes of the struct itself are loaded.

Sample declaration of references in modules:

module: my_module
{
   "kind": "array",
  "name": "people",
  "structure":
  {
    "kind": "struct",
    "name": "people",
    "attributes": [
      {
        "kind": "value",
        "name": "name",
        "type": "s"
      },
      {
        "kind": "reference",
        "name": "partner",
        "type": "my_module.people",
      },
      {
        "kind": "array",
        "name": "children",
        "structure":
        {
          "kind": "reference",
          "name": "children",
          "type": "my_module.people"
        }
      }
    ]
  }
}