add pointers support

[SIGMazer]

Description

This pull request adds comprehensive support for C-style pointers to the Brainrot language, including arbitrary pointer indirection, address-of and dereference operators, pointer assignment, pointer arithmetic, and pointer-based call-by-reference. The changes span the core AST data structures, interpreter logic, and user documentation, ensuring pointers are first-class citizens throughout the system.

Pointer support in AST and interpreter:

• Added pointer_level fields to Variable, Parameter, Function, ReturnValue, Value, and ASTNode structs to track pointer indirection levels, and introduced the Declarator struct for pointer-aware declarations. [1] [2] [3] [4] [5] [6] [7]
• Added support for pointer values (pvalue) to relevant union types and assignment logic, including correct handling of pointer assignment in declarations and assignments. [1] [2] [3] [4] [5] [6]
• Introduced new operator types for address-of and dereference (OP_ADDRESS_OF, OP_DEREFERENCE) and corresponding interpreter logic. [1] [2]
• Added pointer-aware function and parameter creation routines (create_function_ex, create_parameter_ex, etc.) and updated function definition handling to support pointer return types. [1] [2]
• Implemented utility functions for pointer evaluation and address calculation (get_expression_pointer_level, evaluate_expression_pointer, evaluate_lvalue_address, etc.).

Documentation updates:

• Expanded the user guide and language reference to document pointer syntax, semantics, and usage, including pointer declarations, address-of, dereference, pointer assignment, pointer arithmetic, and pointer-based call-by-reference. [1] [2] [3] [4] [5]

Interpreter refactoring:

• Refactored interpreter logic for assignment, declaration, and function definition to handle pointer types and levels, and streamlined loop handling for clarity. [1] [2] [3] [4] [5] [6] [7]

These changes collectively enable robust pointer functionality in Brainrot, closely mirroring C's pointer model for both variable and function handling.

Related Issue

Fixes #95

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Performance improvement
• Refactor

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have documented my changes in the code or documentation
• I have added tests that prove my changes work (if applicable)
• I have run the unit tests locally
• I have run the valgrind memory tests locally
• All new and existing tests pass

[leo-aa88]