Fix some issues with directive definitions

I found some issues with directive definitions:

- I couldn't use `on FIELD_DEFINITION`, I believe because `FIELD` was parsed
  first in `executableDirectiveLocation`. I've combined both
  `executableDirectiveLocation` and `typetypeSystemDirectiveLocation` into one
  function which can reorder them to ensure every directive location gets a fair
  chance at parsing.

Not actually to do with directives, some literals weren't being parsed
correctly.

- The GraphQL spec defines list to be `[]` or `[Value]`, but empty literal lists
  weren't being parsed correctly because of using `some` instead of `many`.

- The GraphQL spec defines objects to be `{}` or `{Name: Value}`, but empty
  literal objects had the same issue.

0 files changed, 0 insertions, 0 deletions