gawk: update to 5.1.1.

Changes from 5.1.0 to 5.1.1
---------------------------

1. Infrastructure upgrades: Bison 3.8, Gettext 0.20.2, Automake 1.16.4,
  and (will wonders never cease) Autoconf 2.71.

2. asort and asorti now allow FUNCTAB and SYMTAB as the first argument if a
  second destination array is supplied. Similarly, using either array as
  the second argument is now a fatal error. Additionally, using either
  array as the destination for split(), match(), etc. also causes a
  fatal error.

3. The new -I/--trace option prints a trace of the byte codes as they
  are executed.

4. A number of subtle bugs relating to MPFR mode that caused differences
  between regular operation and MPFR mode have been fixed.

5. The API now handles MPFR/GMP values slightly differently, requiring
  different memory management for those values. See the manual for the
  details if you have an extension using those values.  As a result,
  the minor version was incremented.

6. $0 and the fields are now cleared before starting a BEGINFILE rule.

7. The duplication of m4 and build-aux directories between the main
  directory and the extension directory has been removed. This
  simplifies the distribution.

8. The test suite has been improved, making it easier to run the entire
  suite with -M. Use `GAWK_TEST_ARGS=-M make check' to do so.

9. Profiling and pretty-printing output has been modified slightly so
  that functions are presented in a reasonable order with respect
  to the namespaces that contain them.

10. Several example programs in the manual have been updated to their
    modern POSIX equivalents.

11. A number of examples in doc/gawkinet.texi have been updated for
    current times. Thanks to Juergen Kahrs for the work.

12. Handling of Infinity and NaN values has been improved.

13. There has been a general tightening up of the use of const and
    of types.

14. The "no effect" lint warnings have been fixed up and now behave
    more sanely.

15. The manual has been updated with much more information about what is
    and is not a bug, and the changes in the gawk mailing lists.

16. The behavior of strongly-typed regexp constants when passed as the
    third argument to sub() or gsub() has been clarified in the code and
    in the manual.

17. Similar to item #4 above, division by zero is now fatal in MPFR
    mode, as it is in regular mode.

18. There have been numerous minor code cleanups and bug fixes. See the
    ChangeLog for details.

(wiz)