gnupg2: security bump to version 2.0.27

Fixes:

CVE-2015-1606: Use after free, resulting from failure to skip invalid packets

CVE-2015-1607: memcpy with overlapping ranges, resulting from incorrect
bitwise left shifts

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>