blur requires memory be aligned.  change the unittest allocator to guarantee 64 byte alignment.
re-enable blur any test that fails if memory is unaligned.

TBR=harryjin@google.com
BUG=libyuv:596,libyuv:594
TESTED=local build passes with row.h removed from tests.

Review URL: https://codereview.chromium.org/2019753002 .