speedo,w32: Install ntbtls as a library

* build-aux/speedo.mk (AUTHENTICODE_FILES): Sign ntbtls files.
(speedo_pkg_ntbtls_configure): Remove duplicated
32 bit entry.
* build-aux/speedo/w32/inst.nsi,
build-aux/speedo/w32/wixlib.wxs: Package ntblts dll.

This changes ntbtls to be built with default options both
on 64 bit and on 32 bit. Previously on 32 bit Windows it
would have been linked statically. But since the file lists
are hardcoded this should be independent of the architecture.