* modify bison syntax to be compatible to v3.02
* modify flex syntax to be compatible to v2.5.35
* Parser
** Pass ASTNodePtr as parameter in each parsing process
** Combine scanning and parsing subroutines into one

* bison/flex
** refactor to reentrant parser
** bridge flex to reentrant parser
** refactor the parser/flex input parameters
*Parser
** Use AST utilities methods
** deprecate some unused classes
*Parser
**reorganize extern variable/functions for bison/flex
**refactor yyerror with fancy ----^ pointing to the error position
**Flex remember current column number before endl
* Walker
** Replace ASTNodePtr with VisitedNodePtr for each spcific node walk
* minor refactor Printer tools
* remove deprecated classes
* revise TODO roadmap