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

fusl/src/ctype/iswcntrl.c

Index: fusl/src/ctype/iswcntrl.c
diff --git a/fusl/src/ctype/iswcntrl.c b/fusl/src/ctype/iswcntrl.c
new file mode 100644
index 0000000000000000000000000000000000000000..daace82a375f46080c1de6c7058a81f29c9b47c7
--- /dev/null
+++ b/fusl/src/ctype/iswcntrl.c
@@ -0,0 +1,17 @@
+#include <wctype.h>
+#include "libc.h"
+
+int iswcntrl(wint_t wc)
+{
+	return (unsigned)wc < 32
+	    || (unsigned)(wc-0x7f) < 33
+	    || (unsigned)(wc-0x2028) < 2
+	    || (unsigned)(wc-0xfff9) < 3;
+}
+
+int __iswcntrl_l(wint_t c, locale_t l)
+{
+	return iswcntrl(c);
+}
+
+weak_alias(__iswcntrl_l, iswcntrl_l);