Circular dependencies

[alejandroclaro]

There are some circular dependencies in the project:

util.js -> xpath.js -> util.js
util.js -> xpath.js -> dom.js -> util.js
xpath.js -> xpathdebug.js ->xpath.js -> util.js

These circular dependencies and issues in the way the 'he' package is imported cause errors when the package is part of a bundle generation in 'iife' or 'umd' formats using rollup.