Based on PR pkg/42846
Changelog:
CHANGES FROM 2.40 to 2.50
* Bug fixes
* New compilation procedure for MVS and CMS
CHANGES FROM 2.30 to 2.40
* Bug fixes from Bill Chatfield
* Updated documentation
* Added support for compiling on CMS (another IBM mainframe OS)
CHANGES FROM 2.20pl2 to 2.30
* Minor bug fixes, cosmetic improvements and portability improvements
* Added support for compiling on MVS (IBM mainframe)
Tested on NetBSD/i3865.99.59 and 5.1.