Fixes a bug in silk_sum_sqr_shift() that was causing issues with Burg.

When an overflow happened in silk_sum_sqr_shift(), the sample pair causing
the overflow would be counted twice. This would lead to the C0 in
silk_burg_modified() being too large and cause problems on loud, tonal
signals. Thanks to Marcello Caramma for tracking down the problem.
1 file changed