The `default` export is treated differently across tooling when transpiled
to CommonJS - tools differ on whether `module.exports` represents the full
module object or just its default export. Switch `src/` modules to named
exports for tooling consistency.
Fixes gh-5262
Closes gh-5292
1. Correct code indentations based on jQuery Style Guide
(contribute.jquery.org/style-guide/js/#spacing).
2. Add rules to "src/.eslintrc.json" to enable "enforcing consistent
indentation", with minimal changes to the current code.
Closes gh-4672
A new `src/deprecated` directory makes it possible to exclude some deprecated
APIs from a custom build when their respective "parent" module is excluded
without keeping that module outside of the `src/deprecated` directory or
the `src/deprecated.js` file.
Closes gh-4572