vala: update to 0.16.0 and restructure some stuff into vala.inc

* SRC_URI is now set initially to real upstream and not freesmartphone.org
* reset PR and INC_PR
* moved DEPENDS += "gtk+" to vala.inc

Signed-off-by: Simon Busch <morphis@gravedo.de>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>