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/mirror/array.cc b/runtime/mirror/array.cc
index 636be33..b92f017 100644
--- a/runtime/mirror/array.cc
+++ b/runtime/mirror/array.cc
@@ -58,8 +58,8 @@
   if (current_dimension + 1 < dimensions->GetLength()) {
     // Create a new sub-array in every element of the array.
     for (int32_t i = 0; i < array_length; i++) {
-      StackHandleScope<1> hs(self);
-      Handle<mirror::Class> h_component_type(hs.NewHandle(array_class->GetComponentType()));
+      StackHandleScope<1> hs2(self);
+      Handle<mirror::Class> h_component_type(hs2.NewHandle(array_class->GetComponentType()));
       Array* sub_array = RecursiveCreateMultiArray(self, h_component_type,
                                                    current_dimension + 1, dimensions);
       if (UNLIKELY(sub_array == nullptr)) {