Provide possibility to select between using a direct and an indirect RTTI reference. This way the references can be changed for selected cases.

ncgrtti, TRTTIWriter:
  * ref_rtti: new "indirect" parameter that's relayed to rtti_mangledname()
  * write_rtti_reference: new "indirect" paramater that's relayed to ref_rtti()

git-svn-id: http://svn.freepascal.org/svn/fpc/branches/svenbarth@28262 3ad0048d-3df7-0310-abae-a5850022a9f2