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

fusl/src/math/rint.c

Index: fusl/src/math/rint.c
diff --git a/fusl/src/math/rint.c b/fusl/src/math/rint.c
new file mode 100644
index 0000000000000000000000000000000000000000..fbba390e7d723774d41ba2a9da74957c20643d63
--- /dev/null
+++ b/fusl/src/math/rint.c
@@ -0,0 +1,28 @@
+#include <float.h>
+#include <math.h>
+#include <stdint.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 rint(double x)
+{
+	union {double f; uint64_t i;} u = {x};
+	int e = u.i>>52 & 0x7ff;
+	int s = u.i>>63;
+	double_t y;
+
+	if (e >= 0x3ff+52)
+		return x;
+	if (s)
+		y = x - toint + toint;
+	else
+		y = x + toint - toint;
+	if (y == 0)
+		return s ? -0.0 : 0;
+	return y;
+}