Figure out when a record needs to be generated as a class

[Therzok]

There are a few scenarios where plain structs were defined as classes in managed land.

Note in this issue the cases where we need to generate a class instead of a struct for Record:

• GList:

  
  // This native struct cannot be expressed in C#. We need to generate a wrapper class for the struct pointer.
  struct List
  {
  void *data;
  List *prev, *next;
  }

// Managed then becomes class List { IntPtr native; // Methods which interact with the native pointer.

 // In case we want to provide unsafe access to the native data
 unsafe struct ListInternal
 {
      IntPtr data;
      ListInternal* prev, next;
 }

 public unsafe ListInternal *Native => (ListInternal *)native;

}