keywording flint 2.3 ~ppc (for singular)

Package-Manager: portage-2.2.10
Enable singular to build against flint. This was a tough commit: Rebased on 3.1.6 from main tree. configuration scripts were broken when flint is installed under
/usr but not anywhere else! The fix for raw ld flags was badly broken when enabling flint. Not sure that it is still needed. If a fix is still needed a better one
then.

Package-Manager: portage-2.2.10