Switch to FreeBSD's actual sincos.

Before:
  BM_math_sin_fast                48 ns         48 ns   14693053
  BM_math_sincos                  61 ns         61 ns   11470219

After:
  BM_math_sin_fast                48 ns         48 ns   14725120
  BM_math_sincos                  43 ns         43 ns   16329843

Bug: N/A
Test: ran tests, benchmarks
Change-Id: I8693c64135233c0641af5302c38748f47ac76737
diff --git a/libm/upstream-freebsd/lib/msun/src/k_sincosf.h b/libm/upstream-freebsd/lib/msun/src/k_sincosf.h
new file mode 100644
index 0000000..ad51e83
--- /dev/null
+++ b/libm/upstream-freebsd/lib/msun/src/k_sincosf.h
@@ -0,0 +1,43 @@
+/*-
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ *
+ * k_sinf.c and k_cosf.c merged by Steven G. Kargl.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD: head/lib/msun/src/k_sincosf.h 319047 2017-05-28 06:13:38Z mmel $");
+
+/* |sin(x)/x - s(x)| < 2**-37.5 (~[-4.89e-12, 4.824e-12]). */
+static const double
+S1 = -0x15555554cbac77.0p-55,	/* -0.166666666416265235595 */
+S2 =  0x111110896efbb2.0p-59,	/*  0.0083333293858894631756 */
+S3 = -0x1a00f9e2cae774.0p-65,	/* -0.000198393348360966317347 */
+S4 =  0x16cd878c3b46a7.0p-71;	/*  0.0000027183114939898219064 */
+
+/* |cos(x) - c(x)| < 2**-34.1 (~[-5.37e-11, 5.295e-11]). */
+static const double
+C0  = -0x1ffffffd0c5e81.0p-54,	/* -0.499999997251031003120 */
+C1  =  0x155553e1053a42.0p-57,	/*  0.0416666233237390631894 */
+C2  = -0x16c087e80f1e27.0p-62,	/* -0.00138867637746099294692 */
+C3  =  0x199342e0ee5069.0p-68;	/*  0.0000243904487962774090654 */
+
+static inline void
+__kernel_sincosdf(double x, float *sn, float *cs)
+{
+	double r, s, w, z;
+
+	z = x * x;
+	w = z * z;
+	r = S3 + z * S4;
+	s = z * x;
+	*sn = (x + s * (S1 + z * S2)) + s * w * r;
+	r = C2 + z * C3;
+	*cs = ((1 + z * C0) + w * C1) + (w * z) * r;
+}