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

fusl/src/math/round.c

+#include "libm.h"
+
+#if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
+#define EPS DBL_EPSILON
+#elif FLT_EVAL_METHOD==2
+#define EPS LDBL_EPSILON
+#endif
+static const double_t toint = 1/EPS;
+
+double round(double x)
+{
+        union {double f; uint64_t i;} u = {x};
+        int e = u.i >> 52 & 0x7ff;
+        double_t y;
+
+        if (e >= 0x3ff+52)
+                return x;
+        if (u.i >> 63)
+                x = -x;
+        if (e < 0x3ff-1) {
+                /* raise inexact if x!=0 */
+                FORCE_EVAL(x + toint);
+                return 0*u.f;
+        }
+        y = x + toint - toint - x;
+        if (y > 0.5)
+                y = y + x - 1;
+        else if (y <= -0.5)
+                y = y + x + 1;
+        else
+                y = y + x;
+        if (u.i >> 63)
+                y = -y;
+        return y;
+}