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

fusl/src/math/frexpl.c

Index: fusl/src/math/frexpl.c
diff --git a/fusl/src/math/frexpl.c b/fusl/src/math/frexpl.c
new file mode 100644
index 0000000000000000000000000000000000000000..3c1b553748eec19a18804362acd508d3877d7fb6
--- /dev/null
+++ b/fusl/src/math/frexpl.c
@@ -0,0 +1,29 @@
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double frexpl(long double x, int *e)
+{
+	return frexp(x, e);
+}
+#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
+long double frexpl(long double x, int *e)
+{
+	union ldshape u = {x};
+	int ee = u.i.se & 0x7fff;
+
+	if (!ee) {
+		if (x) {
+			x = frexpl(x*0x1p120, e);
+			*e -= 120;
+		} else *e = 0;
+		return x;
+	} else if (ee == 0x7fff) {
+		return x;
+	}
+
+	*e = ee - 0x3ffe;
+	u.i.se &= 0x8000;
+	u.i.se |= 0x3ffe;
+	return u.f;
+}
+#endif