Switch class and interface parent as well as extended type to indirect type information

compiler/ncgrtti.pas, TRTTIWriter:
  * write_rtti_data.objectdef_rtti.objectdef_rtti_class_full: use indirect reference for class parent and extended type
  * write_rtti_data.objectdef_rtti.objectdef_rtti_interface_full: use indirect reference for interface parent

rtl/objpas/typinfo.pp, TTypeData:
  + add new method DerefTypeInfoPtr which returns Nil if the indirect reference is Nil and otherwise returns the dereferences indirect reference (for 2.6.x the direct reference is returned as is)
  * rename ParentInfo to ParentInfoRef, HelperParent to HelperParentRef, ExtendedInfo to ExtendedInfoRef, IntfParent ot IntfParentRef and RawIntfParent to RawIntfParentRef and change their type to TypeInfoPtr
  + introduce ParentInfo, HelperParent, ExtendedInfo, IntfParent and RawIntfParent properties that return a PTypeInfo and use the new DerefTypeInfoPtr to return the correct type info value
  * change the other newly introduced properties of TTypeData to use DerefTypeInfoPtr as well to be on the safe side

git-svn-id: http://svn.freepascal.org/svn/fpc/branches/svenbarth@28289 3ad0048d-3df7-0310-abae-a5850022a9f2