Fix nested struct being discarded if parent struct is flagged as partial

[giulianobelinassi]

When clang detects that a certain struct doesn't need a full definition, i.e. its size is not required, then the flag CompleteDefinitionRequired is set to false. But in the following case:

struct Fts3Table {
  struct Fts3Index {
    int nPrefix;
  } *aIndex;
};

int fts3PrefixParameter(
  const char *zParam,
  int *pnIndex,
  struct Fts3Index **apIndex
){
  int a = sizeof(struct Fts3Index);
  return 0;
}

this results in the nested struct Fts3Index not being output as its parent struct Fts3Table is marked as CompleteDefinitionRequired as false. In such cases we have to force CompleteDefinitionRequired of the parent struct as true so that its inner structs can be output.

Fix #77