Remove the damage caused by my bad advice.

The old world never coped with > 32-bit file offsets, Mac OS doesn't have an
off64_t, and we should fix bionic to have _FILE_OFFSET_BITS rather than turd
up all calling code.

Change-Id: I0cb8b1f83fc19ce1fcf51257594551cfd1aa968c
diff --git a/src/file_linux.h b/src/file_linux.h
index 51605e2..3d381d5 100644
--- a/src/file_linux.h
+++ b/src/file_linux.h
@@ -19,8 +19,8 @@
   virtual int64_t Read(void* buffer, int64_t num_bytes);
   virtual int64_t Write(const void* buffer, int64_t num_bytes);
 
-  virtual off64_t Length();
-  virtual off64_t Position();
+  virtual off_t Length();
+  virtual off_t Position();
 
   virtual int Fd() {
     return fd_;