We do this by upscaling the deblocked output as we save it into the
RestorationStripeBoundaries line buffers. (See save_boundary_lines in
restoration.c for the details)

The upscaling is done by calling av1_convolve_horiz_rs, which reads
off the edge of the frame and, of course, across tile boundaries. This
means we need to extend the frame borders before saving boundary
lines (hence the changes to decodeframe.c and encoder.c)

Change-Id: Ia096846898b20afe4737433d772f7277d4f71724