Fix segmentation updates with vp8_set_roimap()

Changes relating to Issue 411

Removed code that was clearing down the segmentation data each
frame.

Added range/parameter checking in vp8_set_roimap(); Return error
if called when cyclic_refresh is enabled.

Correct setup_features() so that it sets or clears the segment update
flags as appropriate.

Change-Id: Ib31ac53006640ddf1ba7b9ec8f8b952e3eff860a