Switch properties to use the indirect type information without breaking backwards compatiblity. :)

compiler/ncgrtti.pas, TRTTIWriter:
  * published_properties_write_rtti_data: use the indirect reference, not the direct one
rtl/objpas/typinfo.pp:
  * to allow compilation with both 2.6.x and 2.7.1 and too avoid too many ifdefs at least in the declarations we define a macro TypeInfoPtr which is either PTypeInfo (2.6.x) or PPTypeInfo (2.7.1 and newer)
  * TPropInfo: rename PropType to PropTypeRef and change type to TypeInfoPtr
  + TPropInfo: add a new property PropType which returns a PTypeInfo out of the PropTypeRef depending on the compiler version

git-svn-id: http://svn.freepascal.org/svn/fpc/branches/svenbarth@28264 3ad0048d-3df7-0310-abae-a5850022a9f2