various legacy and linux-specific stuff

this commit is part of an effort to make more of busybox work
out-of-the-box.

include/sys/sendfile.h

@@ -0,0 +1,16 @@
+#ifndef _SYS_INOTIFY_H
+#define _SYS_INOTIFY_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <unistd.h>
+
+ssize_t sendfile(int, int, off_t *, size_t);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif