Resurrect the post edit invariants checking for fourslash.
Rename some locals.
In Fourslash: Compare ASTs for files produced incrementally versus files produced with a full parse.
Merge branch 'master' into postEditInvariants

Conflicts:
	src/harness/test262Runner.ts
Merge pull request #1467 from Microsoft/postEditInvariants

Resurrect the post edit invariants checking for fourslash.