Bug#877419: reorganize test failure bugs

[Rebecca N. Palmer]

Control: retitle -1 pandas: some I/O tests (hdf5, Stata) fail on non-x86
Control: affects 877754 src:pandas

Using this bug for the I/O test failures and #877754 for the NaN <-> NaT 
test failures.  (The others appear to be fixed already.)

We currently skip many I/O tests because we run the tests in a directory 
that doesn't have the test data, so it is currently unknown whether this 
bug still exists.