core: Change license of logging.[ch] to LGPLv2.1
This file has a long history. I was first written by me in 1998 for
GnuPG under the name logger.c. In 2010 it was renamed to
logging.c. Almost everything was written by me. A few minor fixes are
from g10 Code employees and some other people.
- Signed-off-by: Werner Koch <wk@gnupg.org>