search: do not skip intra tu 32x32 unless TU intra depth is deep (refs #71)

This may not be the best workaround for the bug, and needs a proper long term
fix.
Merge with stable
search: nit
encoder: do not allow scaling lists to be used with 4:4:4 color space (refs #72)

It causes hash mistakes
Merge with stable
encoder: nit, remove obsolete comment