more Gnulib news

[Bruno Haible]

Hi Paul,

Your news entry on http://planet.gnu.org/ is great.

Now, we have accumulated more new features in Gnulib that we can announce.
In order not to fire all news at the same time, I propose one announcement
per week. Alternatingly about things helpful in glibc systems and things
that ensure portability.

For example:
2020-12-08  INT_*_OK macros
2020-12-15  (portability)
2020-12-22  (utility)
2020-12-29  (portability)
2021-01-05  (utility)
2021-01-12  (portability)
2021-01-19  (utility)
...

Topics for portability:
- POSIX substitutes usable in C++
- POSIX and ISO C multithreading across platforms
- clang support
- posix_spawn for native Windows
- stdnoreturn and noreturn modules
- progname and getprogname modules

Topics for utility:
- new containers: set, map, ordered map, stack
- bitset (-> Akim)
- vcs-to-changelog module (-> Siddhesh)
- term-style-control and libtextstyle
- idx module

With all these topics, we can have people's attention until mid-February :)

Bruno