Update to FreeBSD libm r336523.

This includes an ld128 powl, plus the clog* and cpow* families.

Also teach the NOTICE generator to strip SPDX-License-Identifier lines.

Bug: N/A
Test: ran tests
Change-Id: Ic8289d1253666a19468a4088884cf7540f1ec66d
diff --git a/libm/upstream-freebsd/lib/msun/ld128/invtrig.h b/libm/upstream-freebsd/lib/msun/ld128/invtrig.h
index 12f598b..fd1302a 100644
--- a/libm/upstream-freebsd/lib/msun/ld128/invtrig.h
+++ b/libm/upstream-freebsd/lib/msun/ld128/invtrig.h
@@ -1,4 +1,6 @@
 /*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
  * Copyright (c) 2008 David Schultz <das@FreeBSD.ORG>
  * All rights reserved.
  *
@@ -23,7 +25,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * $FreeBSD$
+ * $FreeBSD: head/lib/msun/ld128/invtrig.h 326219 2017-11-26 02:00:33Z pfg $
  */
 
 #include <float.h>