ART: More warnings

Enable -Wno-conversion-null, -Wredundant-decls and -Wshadow in general,
and -Wunused-but-set-parameter for GCC builds.

Change-Id: I81bbdd762213444673c65d85edae594a523836e5
diff --git a/runtime/mem_map.cc b/runtime/mem_map.cc
index 51aba9c..8303f84 100644
--- a/runtime/mem_map.cc
+++ b/runtime/mem_map.cc
@@ -28,7 +28,12 @@
 #endif
 
 #include "base/stringprintf.h"
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wshadow"
 #include "ScopedFd.h"
+#pragma GCC diagnostic pop
+
 #include "thread-inl.h"
 #include "utils.h"