build: Depend on json-glib 0.16.2

Even though we don't need any new symbols from json-glib > 0.14, bump
the required version to 0.16.2 to make sure we are building against the
version of json-glib that's built with the -Bsymbolic linker flag.

Fixes a possible crash in gnome-settings-daemon.

http://blogs.gnome.org/ebassi/2013/09/16/do-not-link-against-pulseaudio-and-json-glib-0-16/
Fix docs build

For details: https://bugzilla.gnome.org/show_bug.cgi?id=701638#c15
Release 3.10.0