vnstat: update to v1.16

Updates vnStat to the latest stable version, drops obsolete patches.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

net/vnstat/patches/990-adjust-configuration-defaults.patch

@@ -0,0 +1,28 @@
+From: Jo-Philipp Wich <jo@mein.io>
+Date: Thu, 26 Jan 2017 15:30:00 +0100
+Subject: [PATCH] config: adjust default values
+
+Adjust the default interval settings to be better suited for slower embedded
+devices.
+
+Signed-off-by: Jo-Philipp Wich <jo@mein.io>
+
+--- a/cfg/vnstat.conf
++++ b/cfg/vnstat.conf
+@@ -87,13 +87,13 @@ DaemonUser ""
+ DaemonGroup ""
+ 
+ # how often (in seconds) interface data is updated
+-UpdateInterval 30
++UpdateInterval 60
+ 
+ # how often (in seconds) interface status changes are checked
+-PollInterval 5
++PollInterval 30
+ 
+ # how often (in minutes) data is saved to file
+-SaveInterval 5
++SaveInterval 30
+ 
+ # how often (in minutes) data is saved when all interface are offline
+ OfflineSaveInterval 30