Editorial: use dot notation for internal methods

[jmdyck]

Specifically, change 19 occurrences of

the [[Foo]] internal method of _O_

and 2 of

_O_'s [[Foo]] internal method

to

_O_.[[Foo]]

and 2 occurrences of

calling the [[Get]] internal method of _obj_ with argument _j_

to

calling _obj_.[[Get]](_j_)

(Split off from #591.)

[bterlson]

I guess this commit includes some previous commits that I squashed into master (should have not squashed it in hindsight, but too late now). You can fix this by either rebasing this branch on top of master or, if there are conflicts, cherry-picking 000be90 on top of master and resetting dots_for_internal_methods to that new commit (or delete that branch and recreate it).

[jmdyck]

Rebased to master (though the process was a bit messy).