bug fixed in AsmGenerator.VisitCast
added test case : test/zen/self-assignment.zen
bug fixed in ZSetNameNode.Append()
Merge branch 'bug-self-assignment'
fix build error
removed unnecessary comment
renewal ZNode class
adding ZListNode for handling variable number of elements
fixed conflict to merge
removed old nodes such as SymbolNode
refactored grammar definition
moved dispatcher to ExpressionPattern
refactoring in deps
remove zen.codegen.debug.ASTGenerator
commit to merge
remove obsolete codes