While working on turning on no-undef I discovered that the various rules we
have for defining globals are a little inconsistent in whether the files they
load recurse through import-globals-from directives and none of them imported
eslint globals directives.

I think we're better off putting all this global parsing code in a single place
rather than spread across multiple rules. Have one rule to turn it on for
parsed files and one function to load globals from other files and make them
share most of the code so we won't get inconsistent. If we find us needing to
turn on/off individual features we can figure out a way to do that in the
future.

This patch does that, the globals.js file does all global parsing with a shared
object that receives events from the AST, either through from an ESlint rule
or from a simple AST walker using estraverse.

MozReview-Commit-ID: 9KQZwsNNOUl

--HG--
extra : rebase_source : 0f1cceca29ac398be97a55bbcd09fe58a8be1435
extra : source : 878db4caf845282f06542793bc4b5c24fa658c14