Generate version.m4 from config.status, in lib/ not lib/m4sugar/.

Generate version.m4 from config.status, in lib/ not lib/m4sugar/.

This simplifies the Makefile a bit and also paves the way for a
bootstrap script (replacing the process of re-running autoreconf with
the just-built autoconf) which will be able to cope with generated
files that get installed in @pkgdatadir@ but not in @pkgdatadir@/m4sugar.

* lib/version.in: New file, contents extracted from lib/local.mk.
* lib/local.mk: Do not generate version.m4 here.
* configure.ac: Generate lib/version.m4 from lib/version.in via
  config.status.

* lib/freeze.mk, lib/local.mk, lib/m4sugar/m4sugar.m4:
  version.m4 now lives in @pkgdatadir@ rather than @pkgdatadir@/m4sugar.