lz4block: No unaligned loads/stores in ARM decoder
lz4block: No unaligned loads/stores in ARM decoder

On ARMv7, unaligned loads work fine, but I think Go still supports ARMv5
and I believe they would crash on that arch.

Performance doesn't suffer greatly (RPI4B):

name                old speed      new speed      delta
UncompressPg1661-4   136MB/s ± 2%   133MB/s ± 2%  -1.65%  (p=0.040 n=10+5)
UncompressDigits-4   262MB/s ± 2%   261MB/s ± 1%    ~     (p=0.679 n=10+5)
UncompressTwain-4    139MB/s ± 4%   136MB/s ± 3%    ~     (p=0.075 n=10+5)
UncompressRand-4     444MB/s ± 5%   451MB/s ± 0%    ~     (p=0.545 n=10+1)

pierrec/lz4