Improve Symbol Table

[TheSYNcoder]

Improvement of Symbol Table

Summary

The current implementation of the symbol tables deletes the lexemes on scope end and thus cannot be used for look-up after the lexer phase.

Solution

A better implementation would be an introduction of visibility flags - to be set to false on scope end rather than deleting.

[noob77777]

Rename symbol table tests from test1, test2 to SymbolTable1, SymbolTable2 ...