Change AddFile method from procedure to boolean function

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@29269 3ad0048d-3df7-0310-abae-a5850022a9f2
Fix for Mantis #27120.

pdecobj.pas, parse_object_members:
  * also allow class fields for helper types

+ added tests

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@29270 3ad0048d-3df7-0310-abae-a5850022a9f2