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/s_sincos.c b/libm/upstream-freebsd/lib/msun/src/s_sincos.c
new file mode 100644
index 0000000..72b2d64
--- /dev/null
+++ b/libm/upstream-freebsd/lib/msun/src/s_sincos.c
@@ -0,0 +1,80 @@
+/*-
+ * ====================================================
+ * 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.
+ * ====================================================
+ * 
+ * s_sin.c and s_cos.c merged by Steven G. Kargl.  Descriptions of the
+ * algorithms are contained in the original files.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD: head/lib/msun/src/s_sincos.c 319047 2017-05-28 06:13:38Z mmel $");
+
+#include <float.h>
+
+#include "math.h"
+#define INLINE_REM_PIO2
+#include "math_private.h"
+#include "e_rem_pio2.c"
+#include "k_sincos.h"
+
+void
+sincos(double x, double *sn, double *cs)
+{
+	double y[2];
+	int32_t n, ix;
+
+	/* High word of x. */
+	GET_HIGH_WORD(ix, x);
+
+	/* |x| ~< pi/4 */
+	ix &= 0x7fffffff;
+	if (ix <= 0x3fe921fb) {
+		if (ix < 0x3e400000) {		/* |x| < 2**-27 */
+			if ((int)x == 0) {	/* Generate inexact. */
+				*sn = x;
+				*cs = 1;
+				return;
+			}
+		}
+		__kernel_sincos(x, 0, 0, sn, cs);
+		return;
+	}
+
+	/* If x = Inf or NaN, then sin(x) = NaN and cos(x) = NaN. */
+	if (ix >= 0x7ff00000) {
+		*sn = x - x;
+		*cs = x - x;
+		return;
+	}
+
+	/* Argument reduction. */
+	n = __ieee754_rem_pio2(x, y);
+
+	switch(n & 3) {
+	case 0:
+		__kernel_sincos(y[0], y[1], 1, sn, cs);
+		break;
+	case 1:
+		__kernel_sincos(y[0], y[1], 1, cs, sn);
+		*cs = -*cs;
+		break;
+	case 2:
+		__kernel_sincos(y[0], y[1], 1, sn, cs);
+		*sn = -*sn;
+		*cs = -*cs;
+		break;
+	default:
+		__kernel_sincos(y[0], y[1], 1, cs, sn);
+		*sn = -*sn;
+	}
+}
+
+#if (LDBL_MANT_DIG == 53)
+__weak_reference(sincos, sincosl);
+#endif