Add tests of special cases for freopen that were omitted from the more
general tests of different modes and similar issues. The special
cases in the three tests here are logically unconnected, it was simply
convenient to put these tests in one patch.
* Test freopen with a NULL path to the new file, in a chroot. Rather
than asserting that this fails (logically, failure in this case is
an implementation detail; it's not required for freopen to rely on
/proc), verify that either it fails (without memory leaks) or that
it succeeds and behaves as expected on success. There is no check
for file descriptor leaks because the machinery for that also
depends on /proc, so can't be used in a chroot.
* Test that freopen and freopen64 are genuinely different in
configurations with 32-bit off_t by checking for an EFBIG trying to
write past 2GB in a file opened with freopen in such a configuration
but no error with 64-bit off_t or when opening with freopen64.
* Test freopen of stdin, stdout and stderr.
Tested for x86_64 and x86.
