Don't generate empty ChangeLog entries, insert the whole message instead.

Don't generate empty ChangeLog entries, insert the whole message instead.

The commits-to-changelog script previously generated ChangeLog entries
with a FIXME if it couldn't find anything applicable for that
particular ChangeLog.  Since we want to use the script for "make dist"
it shouldn't do this.  Instead it now just inserts the whole commit
message in those ChangeLogs.