* scripts/gitlog-to-changelog: New script. Taken from gnulib.
* scripts/git-log-fix: New file.
* scripts/git-log-footer: New file.
* doc/HACKING: Describe the ChangeLog policy
* ChangeLog: New file.
* Makefile.am (EXTRA_DIST): Add new files.
(gen-ChangeLog): New.
(dist-hook): Run gen-ChangeLog.
Rename all ChangeLog files to ChangeLog-2011.
We better do this once and for all instead of cluttering all future
commits with diffs of trailing white spaces. In the majority of cases
blank or single lines are affected and thus this change won't disturb
a git blame too much. For future commits the pre-commit scripts
checks that this won't happen again.