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

fusl/src/string/strncasecmp.c

Index: fusl/src/string/strncasecmp.c
diff --git a/fusl/src/string/strncasecmp.c b/fusl/src/string/strncasecmp.c
new file mode 100644
index 0000000000000000000000000000000000000000..3af5300878a45c2ef78e1063736be9b4de18fd8f
--- /dev/null
+++ b/fusl/src/string/strncasecmp.c
@@ -0,0 +1,18 @@
+#include <strings.h>
+#include <ctype.h>
+#include "libc.h"
+
+int strncasecmp(const char *_l, const char *_r, size_t n)
+{
+	const unsigned char *l=(void *)_l, *r=(void *)_r;
+	if (!n--) return 0;
+	for (; *l && *r && n && (*l == *r || tolower(*l) == tolower(*r)); l++, r++, n--);
+	return tolower(*l) - tolower(*r);
+}
+
+int __strncasecmp_l(const char *l, const char *r, size_t n, locale_t loc)
+{
+	return strncasecmp(l, r, n);
+}
+
+weak_alias(__strncasecmp_l, strncasecmp_l);