Sync libm with upstream FreeBSD.

Upstream SHA 78599c32efed3247d165302a1fbe8d9203e38974.

Test: treehugger
Change-Id: Ib103d211315e320df89a6f0bcb30cd8ba67dd603
diff --git a/libm/upstream-freebsd/lib/msun/bsdsrc/b_tgamma.c b/libm/upstream-freebsd/lib/msun/bsdsrc/b_tgamma.c
index e530649..5cb1f93 100644
--- a/libm/upstream-freebsd/lib/msun/bsdsrc/b_tgamma.c
+++ b/libm/upstream-freebsd/lib/msun/bsdsrc/b_tgamma.c
@@ -1,5 +1,5 @@
 /*-
- * SPDX-License-Identifier: BSD-4-Clause
+ * SPDX-License-Identifier: BSD-3-Clause
  *
  * Copyright (c) 1992, 1993
  *	The Regents of the University of California.  All rights reserved.
@@ -12,11 +12,7 @@
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by the University of
- *	California, Berkeley and its contributors.
- * 4. Neither the name of the University nor the names of its contributors
+ * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
@@ -35,7 +31,7 @@
 
 /* @(#)gamma.c	8.1 (Berkeley) 6/4/93 */
 #include <sys/cdefs.h>
-__FBSDID("$FreeBSD: head/lib/msun/bsdsrc/b_tgamma.c 325966 2017-11-18 14:26:50Z pfg $");
+__FBSDID("$FreeBSD$");
 
 /*
  * This code by P. McIlroy, Oct 1992;