More class linting fixes. Fixes gh-1956

- Pass function name to doFunction() as a string literal or false, rather than as
  a token.
- Do not emit possible strict violation warnings when `this` is used in a class method.
  (`this` is ordinarily either an instance or the class itself).

Fixes gh-1956
does this need to get reset? I expect it doesn't. Patch is tinier without it.