Expose PinnedStatus from Internal

[ndmitchell]

At the moment you can get at UVecBA, but you can't find out if it is pinned or not. Exposing PinnedStatus and isPinned from Foundation,Array.Internal should be sufficient.

[vincenthz]

definitely useful and was already planned.

[vincenthz]

also this is very likely not going to be an internal thing, but something well exposed through a class to do some underlaying memory stuff (e.g. copy which make some sliced array independent). The memory pinning status is something that need to be accessible to make inform choices and people not knowing how specific bits are pinned or not lead to huge problem of fragmentation in two projects I've been working for lately.

[ndmitchell]

Great! As a first step simply exporting the two pinned methods would greatly open up the scope for doing more things on the array, although the only reason I wanted to do that was to copy core foundation code and tweak it (you'll see why later :)).

[vincenthz]

ok. This sounds almost worrying ;)

[ndmitchell]

Everything I did described in #267, so hopefully not that worrying in the end.