Teach release.py to not be so picky about what constitutes out-of-syncness in the branch's CHANGES file by allowing an arbitrary amount of prelude material in the trunk's CHANGES file.  Also, when in verbose mode, print the diffs (if any).
Teach release.py to not be so picky about what constitutes
out-of-syncness in the branch's CHANGES file by allowing an arbitrary
amount of prelude material in the trunk's CHANGES file.  Also, when in
verbose mode, print the diffs (if any).

WARNING:  This has not been purely tested.  (Sorry, Hyrum.)

* tools/dist/release.py
  (fetch_changes, compare_changes): New helper functions.
  (roll_tarballs): Now use compare_changes() instead of a naive 'svn
    diff --summarize'.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion