Log Message:
Add PEGTL 2.8.3

The Parsing Expression Grammar Template Library (PEGTL) is a
zero-dependency C++ header-only parser combinator library for
creating parsers according to a Parsing Expression Grammar (PEG).

Grammars are written as regular C++ code, created with template
programming (not template meta programming), i.e. nested template
instantiations that naturally correspond to the inductive definition
of PEGs (and other parser-combinator approaches).

A comprehensive set of parser rules that can be combined and extended
by the user is included, as are mechanisms for debugging grammars,
and for attaching user-defined actions to grammar rules.