build-erlang: Allow to override attributes.

Such as for example buildPhase, installPhase and more.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
mongooseim: Update to latest Git master branch.

I'm getting quite fed up backporting various patches from master, so
let's jump directly to master and if we get to the state where we have
all features available that we want, then we can still switch to a
release version.

This refreshes the journald patch and also updates cowboy to version
0.8.6 as this is a requirement of the version in master.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>