part to LLVMSourceWriter
change VisitFuncDeclNode to VisitFunctionNode
implement VisitClassDeclNode(for extended class),
VisitNewObjectNode(only user-defined class), and Visit(Getter|Setter)Node
write VisitFuncCallNode for function object(not work)
change to do not use ZFuncType.TypeParams directly
rename GetNowIndentString() to GetCurrentIndentString()
Merge pull request #22 from Kouhei-Moriya/LLVMSourceGen

update LLVMSourceGen