Fix for Mantis #24848. 

ngenutil.pas, AddToStructsInit:
  * don't add class constructors/destructors to the init table if they belong to a generic type

+ test


git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@25234 3ad0048d-3df7-0310-abae-a5850022a9f2