Add a setting that exports all variables by default, regardless of
whether they use the `export` keyword. This includes assignments as well
as parameters.
Just does dependency analysis of variable uses, allowing variables to be
used out of order in assignments, as long as there are no circular
dependencies.
However, use of environment variable is not known to Just, so exported
variables are only exported to child scopes, to avoid ordering dependencies,
since dependency analysis cannot be done.
Just's first parser performed both parsing, i.e the transformation of a
token stream according to the language grammar, and a number of consistency
checks and analysis passes.
This made parsing and analysis quite complex, so this diff introduces a
new, much cleaner `Parser`, and moves existing analysis into a dedicated
`Analyzer`.
Eventually, there will probably be a `crate` visibility specifier that
does the same thing as `pub(crate)`. This commit replaces `pub` with
`pub(crate)`, so when `crate` is available we can easily switch to it.
