Modules which assume the existence of a global variable called "global"
(which exists in Node) are wrapped by Browserify during the build which
normally results in "global" being aliased to "self" or "window" in a
browser environment.

If code on the page into which H is loaded defines a global variable
called "global" however, that gets used instead and this can break such
modules. In the case of https://www.civilsprep.com, "global" is a
reference to a DOM node for example.

This commit fixes the issue by only aliasing "global" (as seen by the
module using it) to either "window" or "self" and not to any existing
variable called "global".

Fixes #2723