When the buffer was separated from the tokenizer, we lost some
validation, including really aggressive carriage return detection.
This brings this back in full force and adds some additional
validation on top of it.
I don't like big monolithic source files, so let's restructure a bit.
parser.zig is still bigger than I would like it to be, but there isn't
a good way to break up the two state machine parsers, which take up
most of the space. This is the last junk commit before I am seriously
going to implement the "streaming" parser. Which is the last change
before implementing deserialization to object. I am definitely not
just spinning my wheels here.
