heap-buffer-overflow in od_mc_predict1fmv8_horizontal_16x16

[tysmith]

Found running commit 4633b81
Built with AddressSanitizer

To reproduce run:
./dump_video test_case.ogv

==51079==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7f759f0e056d at pc 0x000000591721 bp 0x7ffdd538a680 sp 0x7ffdd538a678
READ of size 16 at 0x7f759f0e056d thread T0
    #0 0x591720 in od_mc_predict1fmv8_horizontal_16x16 src/x86/sse2mc.c:368:3
    #1 0x58cf18 in od_mc_predict1fmv8_sse2 src/x86/sse2mc.c:436:5
    #2 0x53b045 in od_mc_predict1fmv src/mc.c:347:3
    #3 0x53b045 in od_mc_predict_singleref src/mc.c:1982
    #4 0x53c3f1 in od_mc_predict src/mc.c:2015:5
    #5 0x55621d in od_state_pred_block_from_setup src/state.c:667:3
    #6 0x55691c in od_state_pred_block src/state.c:719:5
    #7 0x556613 in od_state_pred_block src/state.c:688:5
    #8 0x5565d6 in od_state_pred_block src/state.c:686:5
    #9 0x5579fb in od_state_mc_predict src/state.c:953:9
    #10 0x4f514b in daala_decode_packet_in src/decode.c:1197:5
    #11 0x4ec2de in main examples/dump_video.c:426:13
    #12 0x7f759de5582f in __libc_start_main /build/glibc-GKVZIf/glibc-2.23/csu/../csu/libc-start.c:291
    #13 0x418f98 in _start (daala/dump_video+0x418f98)

test_case.ogv.zip