Log Message:
ntl: update to 11.4.3.

7 years of changes. For details see
https://www.shoup.net/ntl/doc/tour-changes.html

Remove libtool patch. This is too big to be maintained in
pkgsrc and should be upstreamed if deemed interesting enough.

Bump API requirements in bl3.mk because of this change, and
also because HElib (the only consumer of this library in pkgsrc)
needs the new version anyway and will be updated next.