Add helpers include file

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/helpers.h b/helpers.h
new file mode 100644
index 0000000..a3a773b
--- /dev/null
+++ b/helpers.h
@@ -0,0 +1,10 @@
+#ifndef FIO_HELPERS_H
+#define FIO_HELPERS_H
+
+struct in_addr;
+
+extern int __weak posix_memalign(void **ptr, size_t align, size_t size);
+extern int __weak posix_fallocate(int fd, off_t offset, off_t len);
+extern int __weak inet_aton(const char *cp, struct in_addr *inp);
+
+#endif