Add a "fork" of musl as //fusl.

fusl/src/math/__sindf.c

+/* origin: FreeBSD /usr/src/lib/msun/src/k_sinf.c */
+/*
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ * Optimized by Bruce D. Evans.
+ */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+#include "libm.h"
+
+/* |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 */
+
+float __sindf(double x)
+{
+        double_t r, s, w, z;
+
+        /* Try to optimize for parallel evaluation as in __tandf.c. */
+        z = x*x;
+        w = z*z;
+        r = S3 + z*S4;
+        s = z*x;
+        return (x + s*(S1 + z*S2)) + s*w*r;
+}