format::fastxml provides a simple parser of the useful subset of the XML 1.0
(Fifth Edition) specification as defined by the W3C. Features omitted are:

- Support for user-defined entities
- Support for UTF-16 inputs or a UTF-8 BOM
- Any considerations for the "Namespaces in XML 1.0" specification

Attempting to parse an input file which does not conform to the supported subset
of XML will return a syntax error. The purpose of this module is to support most
XML files found in the wild, without supporting the lesser-used features that
lead to problems like "billion laughs" vulnerabilities. If a fully conformant
XML parser is required for your application, you will need to use a third-party
XML implementation. Such an implementation should be able to shadow the standard
library version and present a compatible API.

The API of this module is compatible with format::xml.