Fix: Sanitize XML comment to prevent invalid token errors

[ShobikaG]

Fix Issue#1235: Sanitize XML comment to prevent invalid token errors

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Pull Request Description:

• Added logic to detect and replace any occurrence of "--" in comments with a single "-" to ensure valid XML.
• Used a bulk write ('fwrite') to efficiently handle portions of the string that don't contain invalid sequences.
• Ensured that comments are written correctly without altering the original structure of the code.
• Updated function 'write_spucomment' to handle the sanitization process efficiently.