QAST node types

• QAST::Op - basic operations
• QAST::IVal, QAST::NVal, QAST::SVal - constants
• QAST::Var - variables
• QAST::Stmt - HLL statement
• QAST::Stmts - collection of HLL statements
• QAST::Block - Closures and lexical scopes
• QAST::CompUnit - compilation unit
• QAST::Regex - regex operation