Fix lpegrex.calcline to Correctly Compute Line and Column Numbers

Functionality Changes:

• Position Capping: Ensured that the position does not exceed the length of subject by using math.min(position, #subject) instead of an if statement. This prevents potential out-of-bounds errors.
• Column Number Calculation: Updated the logic to accurately calculate the column number. If the calculated colno is 0, it now correctly assigns position as the column number, ensuring accurate reporting at line boundaries.
• Line End Handling: Improved the determination of lineend by providing a fallback to #subject + 1 when a newline character is not found. This ensures the entire line is captured correctly, especially for the last line in the subject.

Issue:
Fixes #277 - Incorrect line and line number for syntax error.

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Nelua is open source,
but not very open to contributions in the form of pull requests,
if you would like something fixed or implemented in the core language
try first submitting a bug report or opening a discussion instead of doing a PR.
The authors prefer it this way, so that the ideal solution is always provided,
without unwanted consequences on the project, thus keeping the quality of the software.

If you insist doing a PR, typically for a small bug fix, then follow these guidelines:

• Make sure the PR description clearly describes the problem and solution. Include the relevant issue number if applicable.
• Don't send big pull requests (lots of changes), they are difficult to review. It's better to send small pull requests, one at a time.
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• Pull requests just doing style changes are not welcome, a PR must address a real issue.

Motivation

Current version has a very subtle difference in the line number, so its more clear.

Code example

print(

Expected behavior

nelua test.nelua
test.nelua:1:6: syntax error: unclosed parenthesis, did you forget a `)`?

^