Update to FreeBSD libm r336665.

This reverts commit 253a8306316cedfd6fd3e3a169fbffe4cac04035 and moves
us forward to a revision that contains fixes for the problem with the
previous attempt.

This also makes sincos(3)/sincosf(3)/sincosl(3) available to `_BSD_SOURCE`
as well as `_GNU_SOURCE`.

The new FreeBSD libm code requires the FreeBSD `__CONCAT` macro, and all
our existing callers are FreeBSD too, so update that.

There's also an assumption that <complex.h> drags in <math.h> which isn't
true for us, so work around that with `-include` in the makefile. This
then causes clang to recognize a bug -- returning from a void function --
in our fake (LP32) sincosl(3), so fix that too.

Bug: http://b/111710419
Change-Id: I84703ad844f8afde6ec6b11604ab3c096ccb62c3
Test: ran tests
diff --git a/libc/tools/generate-NOTICE.py b/libc/tools/generate-NOTICE.py
index e59fc7a..17429e1 100755
--- a/libc/tools/generate-NOTICE.py
+++ b/libc/tools/generate-NOTICE.py
@@ -96,6 +96,8 @@
         line = re.sub("^ \* ", "", line)
         line = line.replace("** ", "")
         line = line.replace("# ", "")
+        if "SPDX-License-Identifier:" in line:
+            continue
         if line.startswith("++Copyright++"):
             continue
         line = line.replace("--Copyright--", "")