shallowSlice fix

[yuri-kilochek]

When start offset of shallowSlice does not fall on the start of the buffer, and both start and end fall on the same buffer, result contains extra trailing bytes. This happens because buffer start is adjusted first, thus invalidating computed internal end offsets, causing buffer end adjustment to produce incorrect results. Proposed fix simply adjusts first end, then start, as end adjustment has no effect on computed start offsets.

[yuri-kilochek]

Workaround is to replace x.shallowSlice(s, e) with x.shallowSlice(s).shallowSlice(0, e - s).

[mcollina]

Thanks!