Don't use opline->extended_value for FETCH_CLASS flags where it's unnecessary
Embed FETCH_CLASS <string> into the following INSTANCEOF
Fix bug #68224 buffer-overflow in /ext/fileinfo/libmagic/readcdf.c caught by AddressSanitizer

Upstream commit
https://github.com/file/file/commit/f28fbb947e3aa55fc40b09820f59ebff6f66f213
NEWS
Merge branch 'PHP-5.6'

* PHP-5.6:
  NEWS
  Fix bug #68224 buffer-overflow in /ext/fileinfo/libmagic/readcdf.c caught by AddressSanitizer