Log Message:
Update to 2.50

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.