jansson: bump to version 2.12

Update hash of license file (update in year):
https://github.com/akheron/jansson/commit/3e13f514ce5185a057a686221b61d9a9d9e86889



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>