Added a base class for all AST visitors.
Added a base class for all AST visitors.

KonajuGames/CppSharp,inordertotest/CppSharp,nalkaro/CppSharp,imazen/CppSharp,SonyaSa/CppSharp,mono/CppSharp,zillemarco/CppSharp,mohtamohit/CppSharp,xistoso/CppSharp,xistoso/CppSharp,txdv/CppSharp,zillemarco/CppSharp,mohtamohit/CppSharp,inordertotest/CppSharp,genuinelucifer/CppSharp,ktopouzi/CppSharp,ddobrev/CppSharp,mydogisbox/CppSharp,genuinelucifer/CppSharp,Samana/CppSharp,KonajuGames/CppSharp,genuinelucifer/CppSharp,genuinelucifer/CppSharp,u255436/CppSharp,SonyaSa/CppSharp,Samana/CppSharp,mydogisbox/CppSharp,mydogisbox/CppSharp,ddobrev/CppSharp,inordertotest/CppSharp,u255436/CppSharp,KonajuGames/CppSharp,mohtamohit/CppSharp,zillemarco/CppSharp,mono/CppSharp,ktopouzi/CppSharp,KonajuGames/CppSharp,mono/CppSharp,txdv/CppSharp,mydogisbox/CppSharp,zillemarco/CppSharp,u255436/CppSharp,inordertotest/CppSharp,ktopouzi/CppSharp,u255436/CppSharp,mono/CppSharp,ddobrev/CppSharp,genuinelucifer/CppSharp,nalkaro/CppSharp,imazen/CppSharp,Samana/CppSharp,imazen/CppSharp,zillemarco/CppSharp,mydogisbox/CppSharp,imazen/CppSharp,imazen/CppSharp,SonyaSa/CppSharp,mono/CppSharp,mohtamohit/CppSharp,xistoso/CppSharp,SonyaSa/CppSharp,ktopouzi/CppSharp,KonajuGames/CppSharp,mohtamohit/CppSharp,nalkaro/CppSharp,u255436/CppSharp,txdv/CppSharp,xistoso/CppSharp,SonyaSa/CppSharp,Samana/CppSharp,nalkaro/CppSharp,mono/CppSharp,nalkaro/CppSharp,Samana/CppSharp,inordertotest/CppSharp,ktopouzi/CppSharp,xistoso/CppSharp,txdv/CppSharp,ddobrev/CppSharp,txdv/CppSharp,ddobrev/CppSharp