Merge pull request #2811 from bobidle/external_links

docs: Update external links

.github/dependabot.yml

-# Docs: <https://docs.github.com/en/free-pro-team@latest/github/administering-a-repository/customizing-dependency-updates>
+# Docs: <https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/customizing-dependency-updates>
 
 version: 2
 

README.md

 [![Build Gluon](https://github.com/freifunk-gluon/gluon/actions/workflows/build-gluon.yml/badge.svg?branch=master)](https://github.com/freifunk-gluon/gluon/actions/workflows/build-gluon.yml)
-[![License](https://img.shields.io/badge/License-BSD%202--Clause-orange.svg)](https://opensource.org/licenses/BSD-2-Clause)
+[![License](https://img.shields.io/badge/License-BSD%202--Clause-orange.svg)](https://opensource.org/license/bsd-2-clause/)
 [![GitHub release (latest SemVer)](https://img.shields.io/github/v/release/freifunk-gluon/gluon?sort=semver)](https://github.com/freifunk-gluon/gluon/releases/latest)
 
 # Gluon

docs/releases/v2018.1.2.rst

@@ -28,7 +28,7 @@ Bugfixes
   As the path to both config mode and status page were changed between versions
   users could be affected by a redirect to a no more valid URL. 
 
-* batman-adv has received two bugfixes, which were `backported <https://github.com/openwrt-routing/packages/commit/7bf62cc8b556b5046f9bbd37687376fe9ea175bb>`_ from v2018.4
+* batman-adv has received two bugfixes, which were `backported <https://github.com/openwrt/routing/commit/7bf62cc8b556b5046f9bbd37687376fe9ea175bb>`_ from v2018.4
 
 Other changes
 ~~~~~~~~~~~~~

docs/user/mtu.rst

@@ -15,7 +15,7 @@ Consider these key values:
   - and configure `MSS clamping`_ accordingly,
   - and announce your link MTU via Router Advertisements and DHCP
 
-  .. _MSS clamping: https://www.tldp.org/HOWTO/Adv-Routing-HOWTO/lartc.cookbook.mtu-mss.html
+  .. _MSS clamping: https://tldp.org/HOWTO/Adv-Routing-HOWTO/lartc.cookbook.mtu-mss.html
 
 - Encapsulation: Account for the overhead created by the configured mesh protocol
   encapsulating the payload, which is up to 32 Byte (14 Byte Ethernet + 18 Byte