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/jni_env_ext.cc b/runtime/jni_env_ext.cc
index 180e3d7..b2d3835 100644
--- a/runtime/jni_env_ext.cc
+++ b/runtime/jni_env_ext.cc
@@ -28,9 +28,9 @@
 
 static constexpr size_t kLocalsInitial = 64;  // Arbitrary.
 
-JNIEnvExt::JNIEnvExt(Thread* self, JavaVMExt* vm)
-    : self(self),
-      vm(vm),
+JNIEnvExt::JNIEnvExt(Thread* self_in, JavaVMExt* vm_in)
+    : self(self_in),
+      vm(vm_in),
       local_ref_cookie(IRT_FIRST_SEGMENT),
       locals(kLocalsInitial, kLocalsMax, kLocal),
       check_jni(false),