update 1.4.18 (2017-01-01) to 1.4.19 (2021-05-28)
ann: https://lists.gnu.org/archive/html/m4-announce/2021-05/msg00002.html
Includes upstreamed patch for fix-compilation-with-glibc-2.28.patch
NEWS
* Noteworthy changes in release 1.4.19 (2021-05-28) [stable]
** A number of portability improvements inherited from gnulib, including
the ability to perform stack overflow detection on more platforms
without linking to GNU libsigsegv.
* Noteworthy changes in release 1.4.18d (2021-05-11) [beta]
** A number of portability improvements inherited from gnulib.
* Noteworthy changes in release 1.4.18b (2021-05-07) [beta]
** The symbol hash table now defaults to 65537 buckets instead of 509, as
modern systems have enough memory to benefit from fewer hash collisions
by default.
** Introduce the use of gettext, with the immediate benefit of nicer
UTF-8 author names. Over time, more translations of program messages
will become available.
** A number of portability improvements inherited from gnulib.
