Update doxygen to rev 75 via SR 746480
    
    https://build.opensuse.org/request/show/746480
    by user dimstar_suse
    Fixes build for e.g. libftdi1 (see Staging:O)
    
    - Add PR_7193_fix_blank_file_patterns.patch to populate the
      default for FILE_PATTERNS if not set, otherwise no files are
      processed [https://github.com/doxygen/doxygen/issues/7190]
    - Remove obsolete and no longer applying patch:
      doxygen-dot-one-thread.patch (forwarded request 746429 from StefanBruens)