New features added
- add zstd support and the automake option, dist-zstd.
- automake no longer requires a @setfilename in each .texi file
- When cleaning the compiled python files, '\n' is not used anymore in the substitution text of 'sed' transformations.
- For make tags, lisp_LISP is followed by the necessary space when used with CONFIG_HEADERS.
- The automake test txinfo-vtexi4.sh no longer fails when localtime and UTC cross a day boundary.
- Emacsen older than version 25, which require use of byte-compile-dest-file, are supported again.
Signed-off-by: Pierre-Yves <email@example.com>