bug#17429: 24.4.50; __pngconf.h__ in libpng already includes setjmp.h

[Paul Eggert]

> Sven Joachim wrote:
> > |             __pngconf.h__ in libpng already includes setjmp.h;
> > |                      ^

Thanks, that doesn't happen for me on Fedora 20 (libpng16), so I didn't 
run into the problem.  I installed an obvious patch in trunk bzr 117070; 
please give it a try.  I'll take the liberty of marking this bug as done 
to save us all work later; if I'm wrong I'll unmark it.