Add error detection in parser and parsing table.

[noob77777]

Feature Request

Summary

Add error detection in Parser and ParsingTable

Solution

We need to add more error statements in Parser class.
Add support in ParsingTable to detect grammar related errors like non ll(1) grammar.

Checklist

• Add error statements in Parser class
• Add error detection in ParsingTable class
• Make sure incorrect grammar file or input file doesn't cause segmentation faults.