bug#15790: Including php-mode

[Stefan Monnier]

> If you read on, it seems that if somebody relieved Eric of the burden of
> collecting the copyright assignments he'd reconsider.  But looking at
> the list of contributors I'll agree with him that this would be a big
> task.

But those contributors fall into different categories:
- those who contributed ideas but no code.
- those who contributed a small amount of code.
- those who contributed a fairly large amount of code, but most of it
  was copied from some package distributed with Emacs (e.g. from
  cc-mode).
- those who contributed a non-trivial amount of code, but most of it has
  been superseded/replaced since.
- those who have already signed a copyright assignment.
- the others.

Only "the others" need to sign an assignment.  

So the main problem I see is the lack of historical data: the Git
repository only goes back to 2011, so it's going to be difficult to
figure out who contributed what.


        Stefan