Remove empty/obsolete files in top-level directory

[tjanez]

While updating the Fedora par2cmdline package, I've noticed some empty/obsolete files in project's top-level directory:

• NEWS
  • empty file
  • we have ChangeLog
  • does perhaps Autotools force it to exist?
• stamp-h.in
  • empty file
  • does perhaps Autotools force it to exist?
• PORTING
  • content of the file seems to be completely obsolete?
• ROADMAP
  • content of the file was last updated in May 2019 (commits 7d136b9 and d6be95f)
  • how much of it is still relevant today?