Fix conditional obsolete files entry for WITHOUT_EXAMPLES

Add all the files under /usr/share/examples to the MK_EXAMPLES
section. OLD_DIRS entries are not removed if they're not empty so
prior to this change WITHOUT_EXAMPLES didn't have significant effect
on the updated system.

PR: 228484
Submitted by: Dmitry Wagin <dmitry.wagin@ya.ru> (original patch)
MFC after: 1 week