misc Flow library fixes & suppressions

Summary:
The current version of Flow fails to report some errors in library definitions. I'm
working on a Flow fix that would surface these errors. In preparation for this, this diff:

* replaces `FbtErrorListener` (missing) with `IFbtErrorListener` in fbt.js
* fixes typos in several files
* suppresses missing names with `[cannot-resolve-name]`
* adds `sourceMapTarget` option in babel-generator

Changelog: [Internal]

Reviewed By: jbrown215

Differential Revision: D25839533

fbshipit-source-id: 947207db9238aa10663616d59080440d2ac6f243