discover: Reimplement native-parser as a Bison parser

discover: Reimplement native-parser as a Bison parser

Occasionally you look at some code and realise that a) this never gets
built, and b) even if it did it would never compile. Today's example is
native-parser.c which we must have just assumed worked for quite a
while.

The native parser has bitrotted entirely and needs to be brought up to
date. While we're here, lets take the chance to implement a proper
grammar for it. This helps us reason more effectively about the parser,
lets us extend it easily in the future, and.. I wanted to write a Bison
parser too.

This implements most of the old functionality, but drops off some
smaller details like settings icons which needs some separate attention
to bring up to date.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>