Allow to build Gluon with GCC 4.7 (e.g. on Debian Wheezy) as host compiler
again.

Make pkg-config, mkimage and gcc build with GCC 6 as host compiler. Fix
miscompilation of node.

Fixes #755

Should be redundant after 0bd0df6f

LuCI's authentication won't work without rpcd, but we aren't using the
authentication anyways. Users who need it can just install rpcd explicitly.

Fixes #452

Apart from replacing a patch for the former by two patches for latter,
this involved minimal adaptations of the lua scripts in the following
packages:

* gluon-announce
* gluon-announced
* gluon-mesh-batman-adv-core
* gluon-status-page

This also updates batman-adv & alfred to 2015.1

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

Fixes #435

This gets us an up-to-date alfred (and batman-adv 2014.x, as soon as we start to
support it).

The only packages we use from this repo are haveged and (now) fastd and its
dependencies, so we can make the switch safely without updating OpenWrt itself
to Barrier Breaker yet.