This allows bootstrapping in either a development environment (Node.js) or
simply using the intended runtime environment: the user's browser.
* bootstrap.html: Add file (browser).
* bootstrap.js: Add file (command-line).
* bootstrap/Bootstrap.js: Add class. Formalize bootstrap process.
* bootstrap/libprebirth.js
(fsdata): Add variable to serve as filesystem stub.
(fs): Always throw error when `fs' module is unavailable.
($$js$file$_$$g$string): Consider `fsdata'.
* bootstrap/prebirth.js: Export as CommonJS module if in proper
environment. Abort automatic processing via stdin if root CommonJS
module.