[RFC 00/12] Merge value optimized_out and unavailable

["Andrew Burgess" <aburgess at broadcom dot com>]

This patch set merges together how gdb handles values that are
optimized out and values that are unavailable.

I think that in most cases gdb should not care why the contents of
a value are not fetch-able, it is only when we need to display
something to the user that we should have to figure out was this
optimized-out or unavailable?

After this patch set there will be a single unified interface to ask
if a value is available (either fully, partially, or for a range of
bit/bytes), this will answer in terms of both optimized out and
unavailable state.

A second method will fetch the set of flags for the value
optimized/unavailable, this will be used for printing the correct string.

For the implementation I've moved away from the code we currently have
for supporting partially optimized out values and consolidated on the
unavailable vector.

Currently within gdb there are places where we handle optimized out and
unavailable differently, resulting in different style of output, and there
are places where we handle one of optimized out or unavailable, but not the
other.  After this patch set it should (I hope) be much harder for either
of these situations to arise.

Looking forward to your feedback.

Thanks,
Andrew