maint: more authors

[Akim Demaille]

This is by no means "final".  I wrote this quite
quickly, and I certainly forgot someone.
Yet, I meant to include people who contributed significant
changes.  Joel and I already discussed in the past the
possibility of an historical section in the documentation.
This could be a sketch of it.

Also, we could add a short signature in NEWS for each
contribution?  Say JED, AD, PE, PH etc.  If that makes
sense.

For both 2.5 and master.

0003-maint-more-authors.patch
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