Fixes and verifies issue 42

[lemire]

We decoding, our functions may read up to 16 extra bytes from the input (beyond the actual compressed data). Thus the users of this library, for safety, should ensure that there is allocated data 16 bytes beyond the compressed data.

[fzhedu]

@lemire I think we should pad 32 bytes for AVX as the vector lane of AVX is up to 256bits.

[lemire]

@fzhedu We only read into 16-byte registers (so not 32 bytes). However, there may yet still be a bug. Can you share the input that was used to produce this case so we can examine it and produce a fix?

[lemire]

It would be most useful if you can raise this as a new issue.

[lemire]

I do refer you to documentation, this bit is important...

During decoding, the library may read up to STREAMVBYTE_PADDING extra bytes
from the input buffer (these bytes are read but never used).

This requirement could be removed.

[fzhedu]

@fzhedu We only read into 16-byte registers (so not 32 bytes). However, there may yet still be a bug. Can you share the input that was used to produce this case so we can examine it and produce a fix?

ok, I will recheck and test again.