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/optimizing/optimizing_compiler.cc b/compiler/optimizing/optimizing_compiler.cc
index 7f99edb..a590c43 100644
--- a/compiler/optimizing/optimizing_compiler.cc
+++ b/compiler/optimizing/optimizing_compiler.cc
@@ -39,6 +39,7 @@
 #include "nodes.h"
 #include "prepare_for_register_allocation.h"
 #include "register_allocator.h"
+#include "side_effects_analysis.h"
 #include "ssa_builder.h"
 #include "ssa_phi_elimination.h"
 #include "ssa_liveness_analysis.h"