OS PMC should use stat.pasm equivalent indices for stat buffer

[plobsing]

The stat dynop and OS.stat (dynpmc) use inconsistent indices.

OS.stat also does not provide symbolic constants to index into the returned array.

Either the array returned by OS.stat should be re-ordered, or the indices in stat.pasm should reflect the current ordering of the stat buffer as returned by OS.stat and the stat op should be modified.