Assorted adjustments to prepare pg_filedump for its new life.

Assorted adjustments to prepare pg_filedump for its new life.

Add PostgreSQL Global Development Group to the copyright notices, and
remove a couple of no-longer-appropriate references to Red Hat.
Unfortunately I can't undo Red Hat's choice of GPL licensing, but it is
what it is.

Also reduce the pain of version-stamping by coalescing references to the
version into one pair of macros, and removing not-especially-useful
change logs.  IMO the commit logs serve that purpose just as well.