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

fusl/src/math/ceill.c

Index: fusl/src/math/ceill.c
diff --git a/fusl/src/math/ceill.c b/fusl/src/math/ceill.c
new file mode 100644
index 0000000000000000000000000000000000000000..60a83020dd1cb6f6764d0ddb5b64ba9476e71d15
--- /dev/null
+++ b/fusl/src/math/ceill.c
@@ -0,0 +1,34 @@
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double ceill(long double x)
+{
+	return ceil(x);
+}
+#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
+
+static const long double toint = 1/LDBL_EPSILON;
+
+long double ceill(long double x)
+{
+	union ldshape u = {x};
+	int e = u.i.se & 0x7fff;
+	long double y;
+
+	if (e >= 0x3fff+LDBL_MANT_DIG-1 || x == 0)
+		return x;
+	/* y = int(x) - x, where int(x) is an integer neighbor of x */
+	if (u.i.se >> 15)
+		y = x - toint + toint - x;
+	else
+		y = x + toint - toint - x;
+	/* special case because of non-nearest rounding modes */
+	if (e <= 0x3fff-1) {
+		FORCE_EVAL(y);
+		return u.i.se >> 15 ? -0.0 : 1;
+	}
+	if (y < 0)
+		return x + y + 1;
+	return x + y;
+}
+#endif