* Move more specialized expression types from optimizer to AST builder
VarStatement now handles its own value consumption
* Move assign-multisubscript-consume logic to the instruction generator
Adds:
- analyzer/Constants: holds constant name -> value for lookup
- ast/ConstDeclaration: AST node for a const declaration
- optimizer/ConstValidator: validates that an optimized expression is valid to use as a constant.
the Optimizer converts Identifiers that refer to a constant to the optimized constant value.
Adds enough to build the AST nodes for the module function declarations in a .em file.
Adds:
- Function: base class for module function declarations and user functions
- FunctionParameterDeclaration: declaration for a function parameter, as well as its default value if any
- FunctionParameterList: just a holder for function parameter declarations
- ModuleFunctionDeclaration: for function declarations in .em files
- FunctionResolver: hooks up function calls to module functions or user functions
- ModuleProcessor: a visitor for processing const declarations and module function declarations (const declarations are yet to come from the main branch)
