PATCH: fix portability for ext/stdio_filebuf/char/10063-2.cc

[Paolo Carlini]

Loren James Rittle wrote:

> Looking over the history of this extension, I think the test case just
> needs to be slightly tweaked. Paolo, as the new expert in this area, OK?

Eh! So you read the audit trail of 10063...

Unfortunately, I think that's not something as simple as tweaking the
testcases: the whole point of the heroic ;) attempt at fixing 10063
was that we would like to keep on providing a stdio_filebuf intermixing
flawlessly with stdio, because, we discussed off-line this with Benjamin
a bit, we 'promised' that, so to speak...

Clearly, stdio_sync_filebuf works well, Pétur designed it exactly for that
purpose!, that's not the point of the PR...

My strictly personal opinion is that for 3_4 we should make of 
stdio_filebuf.h
an internal header, differently named indeed, and not available anymore
in /ext. That seems to me the only clean and consistent solution. As you
read in the trail, Pétur agrees.

Do you? In case you disagree, what about at least doing that for mainline?

Paolo.