Fix all our unused parameter warnings so we let GCC report them.

There were a couple of genuine bugs here (fixed), plus there's a missing
feature in trace.cc that I've just added a TODO for.

Also note that I haven't touched the compilers; this warning is still
explicitly disabled for that code. I'll do that when there's less going
on in those directories.

Change-Id: Ic3570bf82411a07c7530bfaf1995ac995b9fc00f
diff --git a/src/reflection.cc b/src/reflection.cc
index 6aa239e..a90af0e 100644
--- a/src/reflection.cc
+++ b/src/reflection.cc
@@ -229,7 +229,7 @@
   return false;
 }
 
-void BoxPrimitive(JNIEnv* env, Primitive::Type src_class, JValue& value) {
+void BoxPrimitive(JNIEnv*, Primitive::Type src_class, JValue& value) {
   if (src_class == Primitive::kPrimNot) {
     return;
   }
@@ -275,7 +275,7 @@
   m->Invoke(self, NULL, args, &value);
 }
 
-bool UnboxPrimitive(JNIEnv* env, Object* o, Class* dst_class, JValue& unboxed_value, const char* what) {
+bool UnboxPrimitive(JNIEnv*, Object* o, Class* dst_class, JValue& unboxed_value, const char* what) {
   if (!dst_class->IsPrimitive()) {
     if (o != NULL && !o->InstanceOf(dst_class)) {
       Thread::Current()->ThrowNewExceptionF("Ljava/lang/IllegalArgumentException;",