Recognize reserved words in variable and constant declaration

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If there was a variable declaration that was not followed by a type annotation and the next line started a function declaration, the function declaration was not recognized.

Fixed by including reserved-word-pop before matching the variable identifier.

Resolves #4

I hope this doesn't introduce new problems, but I visually checked it against the included test files and against my own code base and couldn't find a problem.

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Maybe the identifier match in declaration-variable and declaration-constant should also be changed from
- match: '{{identifier}}' to
- match: '{{non_reserved_identifier}}'.

Then - include: reserved-word-pop can be moved to the end before - include: else-pop.

[blach]

I've updated the pull request with a new commit that uses - match: '{{non_reserved_identifier}}.