mawk: update to 20200120

20200120
+ resync with my-autoconf.
+ fix typos found with codespell.
+ when reading input in interactive mode, provide for extending the
  buffer size for very long lines (Original-Mawk #59).

20200106
+ correct line-number shown in too-many-arguments error message for
  the case where the function is a forward reference (report by
  "mukti").
+ fix install for manpage when configure --srcdir option is used
  (report by Rajeev V Pillai).
+ use both CFLAGS/LDFLAGS when linking in makefile (report by
  Rajeev V Pillai).
+ fix clang-9 warning in bi_funct.c (report by Rajeev V Pillai).
+ minor improvement to gcc warning options, from vile

20191231
+ updated configure macros
+ update config.guess and config.sub

20190203
+ improve manpage formatting, e.g., for man2html
+ improve debug-traces

20190129
+ eliminate non-portable tdestroy() from zmalloc no-leaks code.
+ updated configure macros
+ update config.guess and config.sub

20181114
+ revert a change for memory-leaks which made the forced-exit via a
  user function inconsistent with earlier versions (report by Sihera
  Andre).
+ amend a change for memory-leaks to avoid a double-free (Original-Mawk
  #56).

(gutteridge)