This removes PKG_VERSION and PKG_RELEASE from most Makefiles, as the
value was never useful for Gluon packages; instead, PKG_VERSION is set
to 1 in gluon.mk.

It also removes two other weird definitions:

- gluon-iptables-clamp-mss-to-pmtu replicating the old PKG_VERSION logic
  from gluon-core, but without the fixed PKG_BUILD_DIR to prevent
  unnessary rebuilds
- gluon-hoodselector set GLUON_VERSION=3

gluon-mesh-babel conigures babeld and thus the mesh. This mesh is only usable
with routes to the clients which are discovered by l3roamd.

Rename to respondd.c / respondd.so, gluon.mk expects these names. This way
we can remove the install code. The installed filename is changed to
gluon-mesh-babel.so, bringing it in line with out common naming scheme.