Context-free grammar tools for ATS.

• grm: a typeful in-memory context-free grammar representation
• grmfuncs: efficient implementations of FIRST/FOLLOW-set computation for a given grammar
• utils/ltab: compact lookup hash table
• utils/fundigraph: directed graph representation with strongly-connected components and efficient reflexive, transitive closure algorithms

TODO

The whole thing doesn't build yet, but the tests do. Please see the src/TEST subdirectory.

1. refactoring: make grm use the new symbol data type (already exists in a separate module)
2. implement code for doing constructions of automata (LR0, LR1, LALR1, LL1, etc.)
3. implement lexers/parsers for various inputs to grm (JSON format, something with yacc/lex compat, etc.)
4. implement different "plug-in" modules for outputting automata (as JSON/XML, as executable code -- ATS code, etc.)
5. compile to WebAssembly, make it available on a webpage ("enter your grammar here, have it converted to whatever you want!")