Revert "Remove the prebuilt bionic headers."

This reverts commit 8505def823922e45e94d1047499ea973346c95e7.

Reason for revert: Darwin sucks

Change-Id: I495b8a43bae9f3bf813329ec9ea7ae859e6ab456
diff --git a/headers/endian.h b/headers/endian.h
new file mode 100644
index 0000000..65e2930
--- /dev/null
+++ b/headers/endian.h
@@ -0,0 +1 @@
+#include <sys/endian.h>