[Perl/perl5] 4e81aa: Add boolean cast to ndbm_EXISTS

[Dagfinn Ilmari Mannsåker via perl5-changes]

  Branch: refs/heads/ndbm-exists-bool
  Home:   https://github.com/Perl/perl5
  Commit: 4e81aa1db1617d7aee72313f00a3d75f9a005d44
      
https://github.com/Perl/perl5/commit/4e81aa1db1617d7aee72313f00a3d75f9a005d44
  Author: Dagfinn Ilmari Mannsåker <ilm...@ilmari.org>
  Date:   2023-08-08 (Tue, 08 Aug 2023)

  Changed paths:
    M ext/NDBM_File/NDBM_File.pm
    M ext/NDBM_File/NDBM_File.xs

  Log Message:
  -----------
  Add boolean cast to ndbm_EXISTS

The AIX compiler yields a warning when assigning the void* from
dbm_fetch(...).dptr to the bool RETVAL, so wrap the call in
cBOOL(...).