configury: lua modules should install to luaexec_LTLIBRARIES.

* Makefile.am (luaexec_LTLIBRARIES): Set this for appending to
from included make fragments, because we want `make install` to
put modules into e.g. /usr/local/lib/lua/5.3, not /usr/local/lib.
* NEWS: Updated.
Reported by Dennis Schridde <devurandom@gmx.net>

Signed-off-by: Gary V. Vaughan <gary@gnu.org>