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

fusl/src/math/fmaxl.c

Index: fusl/src/math/fmaxl.c
diff --git a/fusl/src/math/fmaxl.c b/fusl/src/math/fmaxl.c
new file mode 100644
index 0000000000000000000000000000000000000000..4b03158e06292b28576615a2a1dd36bd6bf1d34a
--- /dev/null
+++ b/fusl/src/math/fmaxl.c
@@ -0,0 +1,21 @@
+#include <math.h>
+#include <float.h>
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double fmaxl(long double x, long double y)
+{
+	return fmax(x, y);
+}
+#else
+long double fmaxl(long double x, long double y)
+{
+	if (isnan(x))
+		return y;
+	if (isnan(y))
+		return x;
+	/* handle signed zeros, see C99 Annex F.9.9.2 */
+	if (signbit(x) != signbit(y))
+		return signbit(x) ? y : x;
+	return x < y ? y : x;
+}
+#endif