strtok_r: relax license to LGPLv2+

strtok_r: relax license to LGPLv2+

strtok_r borrows from glibc, which is LGPLv2+; besides, the
only major changes since 2007-10, when LGPLv3 became the default,
were in commit 5985805, to work around a glibc header bug.

* modules/strtok_r (License): Relax license.
Reported by Matthias Bolte.

Signed-off-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 7c1b995a7041ea366acafeb8632e1080f349f03f)