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
Moving the scripts to a common directory not only vastly simplifies the
zzz-gluon-upgrade script, but also allows to define an ordering of such
scripts across packages.
