elang: Apply clang-format
elang/compiler: Introduce |ast::VarStatment| for representing parameter of method.
elang/compiler: Introduce 'return' statement parser along with |ast::BlockStatement| and |ast::ReturnStatement| AST nodes.
elang/compiler: Simplify equality check for |Token*| with |TokenType|.
elang/compiler: Introduce "if" parser along with |ast::IfStatement| node.
elang/compiler: Rename |Parser::DeclarationSpace| to |Parser::LocalDeclarationSpace|.
elang/compiler: Move statement parers into thier own functions.
elang/compiler: Introduce "do" statement parser.