Fixes and changes to aid in porting from the original OpenBSD sources

[ssolie]

A bunch of changes to prepare to merge even more changes from OpenBSD.

• Reformatted history and fixed contact info.
• Fixed contact command to point to new github home.
• Fixed Makefile to produce sh.debug to aid in debugging.
• Removed unused attrib.h file.
• Removed proto.h file and merged into sh.h to align with
  OpenBSD ksh 5.2.14.
• Merged in memory allocation module from OpenBSD ksh 5.2.14.
• Merged changes to eliminate EXTERN define from OpenBSD ksh 5.2.14.
• Replaced global struct env *e with more explicit *genv as in
  OpenBSD ksh 5.2.14.