Parser Tools: lex and yacc-style Parsing (BR edition)

This documentation assumes familiarity with lex- and yacc-style lexer and parser generators.

This is a fork of the parser-tools package. It has a variety of small improvements and bugfixes designed to support the brag parser language, in particular the srcloc structure type (e.g., lexer-srcloc). But the core lexing and parsing engines are identical.