Disable cyclic refresh if ROI is used and add flag to properly handle
the static_thresh deltas.
Remove the ROI test for cyclic refresh (it's allowed but disabled if ROI
is used).
Add an example in vpx_temporal_svc_encoder.c. Turned off by default.

BUG=webm:1470

Change-Id: Ief9ba1d7f967bc00511b412b491c3f70943bfbda