headers: relax license to LGPLv2+

headers: relax license to LGPLv2+

The replacement headers deserve relaxed licenses, even if the
functions they declare cannot be accessed without a tighter license.

See the list archives for consensus on this action.

* modules/fcntl-h (License): Relax license.
* modules/getopt-posix (License): Likewise.
* modules/locale (License): Likewise.
* modules/math (License): Likewise.
* modules/pty (License): Likewise.
* modules/sched (License): Likewise.
* modules/search (License): Likewise.
* modules/spawn (License): Likewise.
* modules/stdarg (License): Likewise.
* modules/sysexits (License): Likewise.

Signed-off-by: Eric Blake <eblake@redhat.com>