Improve Dottydoc error reporting

[TheElectronWill]

Before: incorrect line number and unclear error message
Example (from #7326):

-- Error: doc/UserGuide.md:1:6 -------------------------------------------------
1 |## ScalaCheck User Guide
  |      ^
  |      unexpected token 'token  57', expected: 'token  77'

After: token ids translated to name or symbol+name, and fixed line number

-- Error: docs/UserGuide.md:907:6 ----------------------------------------------
907 |   *  def canCreateNewSut(newState: State, initSuts: Traversable[State]
    |      ^
    |      unexpected Id, expected '}}' (OutEnd)

[smarter]

Thanks!