TLAPM syntax parser does not accept prefix operators as higher-level operator parameters

[ahelwer]

This also affects the infix minus operator -, probably because it is caught up in some logic involving the negative prefix operator -. Both these tests will fail:

---- MODULE Test ----
op == f(
  ~,
  \lnot,
  \neg,
  UNION,
  SUBSET,
  DOMAIN,
  -.,
  ENABLED,
  UNCHANGED,
  [],
  <>
)
====

---- MODULE Test ----
op == f ( - )
====

Ref #159