Fix handling of "allow fds" state.

Didn't take into account nesting of bundles.  Boo.

Change-Id: Ic8cf21ad8d6f4938a3e105128624c9d162310d01
diff --git a/include/binder/Parcel.h b/include/binder/Parcel.h
index d973785..3fa2acb 100644
--- a/include/binder/Parcel.h
+++ b/include/binder/Parcel.h
@@ -59,7 +59,8 @@
     status_t            appendFrom(const Parcel *parcel,
                                    size_t start, size_t len);
 
-    bool                setAllowFds(bool allowFds);
+    bool                pushAllowFds(bool allowFds);
+    void                restoreAllowFds(bool lastValue);
 
     bool                hasFileDescriptors() const;