C-syntax-validator

This allows python scripts to invoke the API without calling out to an external java process.

It takes about 1.3 ms to parse an expression with the new API, it takes 80 ms to call out to
the old java process (likely due to JVM warmup).

Allows parsing:
- Expression
- Statement
- Block body (no braces)
- Whole file/compilation unit (default)

Before this the utility was limited to parsing a whole file
at a time (the last option).

Simple wrapper around the C grammar available here: https://github.com/antlr/grammars-v4

Doesn't do much besides parsing command line arguments and passing to ANTLR.

This was written in Java instead of Go, because the go binary was 5MB.......