Add new procedure option: po_syscall_has_libsym,
 include this option only of libsym field
 is non NIL.
 Use this option to only write redef of libsym if needed.
 Adapt ppudump source to this new procedure option.


git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@28732 3ad0048d-3df7-0310-abae-a5850022a9f2