edoc: Fix building of documentation in sub directories

8115c0840527 broke building for projects that used sub directories
(but not packages).
Use ~ts for filenames
[edoc] Fix a bug involving a type declaration and a comment
Merge branch 'hb/edoc/bug_fix/OTP-10866'

* hb/edoc/bug_fix/OTP-10866:
  [edoc] Fix a bug involving a type declaration and a comment
Update copyright years
Prepare release