Move code around and address growable_array comment.

- Move SideEffectsAnalysis to its own file.
- Move most of gvn.h to gvn.cc.
- Don't call Resize in GrowableArray constructor, but just set num_used
  directly.

Change-Id: I1f1291207945d678d3c99cc0ec1ec155bcae82f6
diff --git a/compiler/utils/growable_array.h b/compiler/utils/growable_array.h
index b848429..6af4853 100644
--- a/compiler/utils/growable_array.h
+++ b/compiler/utils/growable_array.h
@@ -40,8 +40,7 @@
     GrowableArray(ArenaAllocator* arena, size_t init_length, T initial_data)
       : arena_(arena),
         num_allocated_(init_length),
-        num_used_(0) {
-      SetSize(init_length);
+        num_used_(init_length) {
       elem_list_ = static_cast<T*>(arena_->Alloc(sizeof(T) * init_length,
                                                  kArenaAllocGrowableArray));
       for (size_t i = 0; i < init_length; ++i) {