jansson: json_pack with new format to verify required runtime version.

Add a json_pack at startup that will fail if runtime links against a
library older than jansson-2.11.

Change-Id: I101aebafe0f9407650206f7c552dad3d69377b5a

main/asterisk.c

@@ -4059,7 +4059,7 @@ static void asterisk_daemon(int isroot, const char *runuser, const char *rungrou
 	}
 	ast_verb(0, "PBX UUID: %s\n", pbx_uuid);
 
-	ast_json_init();
+	check_init(ast_json_init(), "libjansson");
 	ast_ulaw_init();
 	ast_alaw_init();
 	tdd_init();