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
9 files changed