Further change to mv reference search.

Further change to mv reference search.

This experimental change reorders the search so
that all possible references that match the target
reference frame are tested first and these in order
of distance from the current block. These will usually
be the highest scoring candidates.

If we do not find enough good candidates this way
we try non matching cases. These will usually be lower
scoring candidates.

The change in order together with breakouts when
we have found enough candidates should reduce
the computational cost and especially reduce the number
of sort operations.

Quality Results:
Std Hd +0.228%, Hd +0.074%, YT +0.046%, derf +0.137%

This effect is probably due to the fact that more distant
weak candidates are now less likely to get "promoted" over
near candidates even if they are repeated.

Change-Id: Iec37e77d88a48ad0ee1f315b14327a95d63f81f6