batman-adv: decrease maximum fragment size

This should workaround batman-adv's inability to deal with different MTUs
which need fragmentation.

Fixes #435

patches/packages/routing/0003-batman-adv-decrease-maximum-fragment-size.patch

+From: Matthias Schiffer <mschiffer@universe-factory.net>
+Date: Thu, 6 Aug 2015 21:29:47 +0200
+Subject: batman-adv: decrease maximum fragment size
+
+diff --git a/batman-adv/patches/1000-batman-adv-decrease-maximum-fragment-size.patch b/batman-adv/patches/1000-batman-adv-decrease-maximum-fragment-size.patch
+new file mode 100644
+index 0000000..a93b9fa
+--- /dev/null
++++ b/batman-adv/patches/1000-batman-adv-decrease-maximum-fragment-size.patch
+@@ -0,0 +1,11 @@
++--- a/main.h
+++++ b/main.h
++@@ -148,7 +148,7 @@ enum batadv_uev_type {
++ /* Maximum number of fragments for one packet */
++ #define BATADV_FRAG_MAX_FRAGMENTS 16
++ /* Maxumim size of each fragment */
++-#define BATADV_FRAG_MAX_FRAG_SIZE 1400
+++#define BATADV_FRAG_MAX_FRAG_SIZE 1280
++ /* Time to keep fragments while waiting for rest of the fragments */
++ #define BATADV_FRAG_TIMEOUT 10000
++