C++: Missing return-value check for scanf-like functions #1076

[d10c]

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• Update .gitignore for .vscode/*.log temporaries
• C++: Add test and placeholder query.
• C++: First working. We now prefer flagging the cases where the variable was initialized, as in real world cases we haven't seen it done safely.
• Add more (false-negative) MissingCheckScanf tests
• Add more MissingCheckScanf test cases