[doc] Add Martin Jambor and Michael Matz to contrib.texi

[Jakub Jelinek]

On Sun, Apr 12, 2015 at 10:34:06PM +0200, Gerald Pfeifer wrote:
> ...a Honza/Gerald co-production. :-)  Applied.
> 
> Jakub, is this (and another one I should have in the next few
> days) okay to backport even after RC1?

Yes, thanks.

> 2015-04-12  Jan Hubicka  <hubicka@ucw.cz>
> 	    Gerald Pfeifer  <gerald@pfeifer.com>
> 
> 	* doc/contrib.texi (Contributors): Add Martin Jambor and
> 	Michael Matz.

	Jakub