Switch over to the google3 unix_file File*.

I also moved macros.h to base/macros.h to ease google3 porting, at
the expense of a larger than necessary change. (I learned my lesson,
though, and didn't make the equivalent base/logging.h change.)

I'm not sure whether we want to keep the unix_file MappedFile given
our existing MemMap, but it's easier to bring it over and then remove
it (and possibly revert the removal) than to bring it over later.

Change-Id: Id50a66faa5ab17b9bc936cc9043dbc26f791f0ca
diff --git a/src/class_linker.cc b/src/class_linker.cc
index 9a354e1..97b25ba 100644
--- a/src/class_linker.cc
+++ b/src/class_linker.cc
@@ -27,6 +27,7 @@
 #include <utility>
 #include <vector>
 
+#include "base/unix_file/fd_file.h"
 #include "casts.h"
 #include "class_loader.h"
 #include "debugger.h"