[PATCH] Always do locking when accessing streams (bug 15142, bug 14697)

[Florian Weimer]

* Andreas Schwab:

> Now that abort no longer calls fflush there is no reason to avoid locking
> the stdio streams anywhere.  This fixes a conformance issue and potential
> heap corruption during exit.  The test nptl/tst-stdio1 is removed as that
> was expecting the problematic behaviour.

I'm not sure if the justification is correct.  We don't know if there
are programs which call flockfile on some file and expect exit to
still work (and terminate the program), which is part of what
nptl/tst-stdio1 tests.

If there are such programs, we may need to make the new behavior
conditional on a new symbol version for exit.  But I guess we can put
in your patch now and see if testing shows any problems.