links: upgrade to 2.7 to fix build with libpng-1.5

* cookies api changed between 2.1pre30 and 2.7
* LIC_FILES_CHKSUM changed because of formal change
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<     This program is free software; you can redistribute it and/or modify
---
>     on, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
>     USAThis program is free software; you can redistribute it and/or
>     modify

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>