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
Specify conffiles for our packages, so they aren't overwritten during
opkg updates. While this only matters during development, it is
unintended to have different behaviour for opkg update and full firmware
updates.