Relicense some modules under LGPLv2+. Paul Eggert's approval is in http://lists.gnu.org/archive/html/bug-gnulib/2016-11/msg00037.html. Eric Blake's approval is in http://lists.gnu.org/archive/html/bug-gnulib/2016-11/msg00042.html. Ludovic Courtès's approval is in http://lists.gnu.org/archive/html/bug-gnulib/2016-11/msg00038.html. * modules/isnand-nolibm (License): Change to LGPLv2+. * modules/isnanf-nolibm (License): Likewise. * modules/isnanl-nolibm (License): Likewise.