...unclear about how to use stmt and type class
add files.
debug some error
add some functions in symboltable.h
claim symtab structure
fix errors
tempelately commit! doing testing now!
10:10, June 21, debuging
add the 'miss' const_value_node ==> fix expression error!
fix var-val funcion
Merge branch 'symtab'

Conflicts:
	src/bison/pascal.y
	src/node/DeclNode.hpp
	src/node/ExpNode.hpp
	src/node/ModuleNode.hpp
	src/node/StmtNode.hpp
	src/node/TreeNode.hpp
	src/pascal.tab.c
	src/pascal.tab.h