test suite failures with 1.4.0

The cross-Linux portability stress test, also known as "autobuilding on
all 12 of Debian's supported hardware architectures", shows a couple of
testsuite failures. Of the 9 architectures with a useful build log so
far, 5 passed and 4 failed:

  i386 ok
  amd64 ok
  sparc ok
  s390 ok
  powerpc ok
  ia64 FAIL: lt-fs-base-test 2: open an existing Berkeley DB filesystem
  alpha FAIL: switch_tests.py 17: refresh the WC file system read-only
                                      attribute
  mips FAIL: switch_tests.py 17: (ditto)
  mipsel FAIL: switch_tests.py 17: (ditto)

Full build logs, including 'cat tests.log' when a test failed:

  http://buildd.debian.org/build.php?pkg=subversion

It's of course possible that the failures are intermittent and the
specific set of architectures don't matter. They don't show any
obvious pattern of architecture dependence - big- and little-endian,
32- and 64-bit. Also, I note that sparc, which tends to be bothered by
memory alignment issues, came out fine.

FAIL: lt-fs-base-test 2: open an existing Berkeley DB filesystem
FAIL: switch_tests.py 17: refresh the WC file system read-only attribute