symdef.pas, tstoreddef:
  * adjust "is_generic" so that it will really work for true generics only
  + added an analogous method "is_specialization" for specializations

Both methods are not used yet, but this will change in the future...

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@23348 3ad0048d-3df7-0310-abae-a5850022a9f2