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

Installing the script into the image allows site checks to run for
manual package installations via opkg.

A leading tab character usually marks recipe lines in Makefiles;
non-recipe lines must be indented using spaces.

The incorrect tab character doesn't seen to have caused any issues in
this case, but it should be fixed nonetheless, if only for consistency.

- If luasrcdiet fails for a Lua script, this is a bug that should be
  noticed rather than including the unminified script
- Use .tmp suffix for temporary file rather than .o
- Replace chmod + stat + mv with simpler cp + rm to overwrite file while
  preserving file mode

We don't use anything else from luci-base anymore.

The code is slightly cleaned up to fix compiler warnings.

Our provider modules are prefixed with gluon- now, and the log message
about a missing provider dir was confusing users.

Ensure packages get rebuilt when gluon.mk changes.

The gluon-web package is basically a stripped-down and refactored version
of the LuCI base.

This call takes an input and an output argument and will copy all files
from the input to the output, while minifying the Lua files.

[Matthias Schiffer: simplified definition, added commit message.]