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

fusl/src/math/__fpclassifyl.c

Index: fusl/src/math/__fpclassifyl.c
diff --git a/fusl/src/math/__fpclassifyl.c b/fusl/src/math/__fpclassifyl.c
new file mode 100644
index 0000000000000000000000000000000000000000..481c0b949974ad43a59e95846bf9fb83ff5cbf23
--- /dev/null
+++ b/fusl/src/math/__fpclassifyl.c
@@ -0,0 +1,34 @@
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+int __fpclassifyl(long double x)
+{
+	return __fpclassify(x);
+}
+#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
+int __fpclassifyl(long double x)
+{
+	union ldshape u = {x};
+	int e = u.i.se & 0x7fff;
+	int msb = u.i.m>>63;
+	if (!e && !msb)
+		return u.i.m ? FP_SUBNORMAL : FP_ZERO;
+	if (!msb)
+		return FP_NAN;
+	if (e == 0x7fff)
+		return u.i.m << 1 ? FP_NAN : FP_INFINITE;
+	return FP_NORMAL;
+}
+#elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384
+int __fpclassifyl(long double x)
+{
+	union ldshape u = {x};
+	int e = u.i.se & 0x7fff;
+	u.i.se = 0;
+	if (!e)
+		return u.i2.lo | u.i2.hi ? FP_SUBNORMAL : FP_ZERO;
+	if (e == 0x7fff)
+		return u.i2.lo | u.i2.hi ? FP_NAN : FP_INFINITE;
+	return FP_NORMAL;
+}
+#endif