redundant ChangeLog header lines

[Roland McGrath]

When you're adding a new log entry and the header line (the one with
the date and your name) would be identical to the existing top header
line in the file, then don't add a new header line.  The header lines
are only there to show when the information they contain (date, name,
email) differs from the previous entry (i.e. the one immediately
following in the file).  

Two logically-separate changes are indicated just by being in two
different paragraphs (i.e. having a blank line between them).  When
you do a bunch of changes that all go together (in one commit--because
they are logically related and you can't build successfully with one
and not the other), you should not have blank lines in the middle of
the log entries for all those changes.


Thanks,
Roland