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/reflection_test.cc b/runtime/reflection_test.cc
index f8e0f47..eca1800 100644
--- a/runtime/reflection_test.cc
+++ b/runtime/reflection_test.cc
@@ -115,8 +115,8 @@
       *receiver = nullptr;
     } else {
       // Ensure class is initialized before allocating object
-      StackHandleScope<1> hs(self);
-      Handle<mirror::Class> h_class(hs.NewHandle(c));
+      StackHandleScope<1> hs2(self);
+      Handle<mirror::Class> h_class(hs2.NewHandle(c));
       bool initialized = class_linker_->EnsureInitialized(self, h_class, true, true);
       CHECK(initialized);
       *receiver = c->AllocObject(self);