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

fusl/include/features.h

Index: fusl/include/features.h
diff --git a/fusl/include/features.h b/fusl/include/features.h
new file mode 100644
index 0000000000000000000000000000000000000000..3cc3e57933e1ae67c295e70d6108bb1b86b11f8f
--- /dev/null
+++ b/fusl/include/features.h
@@ -0,0 +1,36 @@
+#ifndef _FEATURES_H
+#define _FEATURES_H
+
+#if defined(_ALL_SOURCE) && !defined(_GNU_SOURCE)
+#define _GNU_SOURCE 1
+#endif
+
+#if defined(_DEFAULT_SOURCE) && !defined(_BSD_SOURCE)
+#define _BSD_SOURCE 1
+#endif
+
+#if !defined(_POSIX_SOURCE) && !defined(_POSIX_C_SOURCE) \
+ && !defined(_XOPEN_SOURCE) && !defined(_GNU_SOURCE) \
+ && !defined(_BSD_SOURCE) && !defined(__STRICT_ANSI__)
+#define _BSD_SOURCE 1
+#define _XOPEN_SOURCE 700
+#endif
+
+#if __STDC_VERSION__ >= 199901L
+#define __restrict restrict
+#elif !defined(__GNUC__)
+#define __restrict
+#endif
+
+#if __STDC_VERSION__ >= 199901L || defined(__cplusplus)
+#define __inline inline
+#endif
+
+#if __STDC_VERSION__ >= 201112L
+#elif defined(__GNUC__)
+#define _Noreturn __attribute__((__noreturn__))
+#else
+#define _Noreturn
+#endif
+
+#endif