Add visualization of CU blocks for mode searching.
Add visualization of CU blocks for mode searching.

This is for debugging the inter movement vector search.

ultravideo/kvazaar,lu-zero/kvazaar,ultravideo/kvazaar,lu-zero/kvazaar,ultravideo/kvazaar,lu-zero/kvazaar,ultravideo/kvazaar,ultravideo/kvazaar,lu-zero/kvazaar