Inappropriate use of QSKIP in QFile autotest

In qtbase/tests/auto/corelib/io/qfile/tst_qfile.cpp, the tailFile() test function is disabled with:

QSKIP("File change notifications are so far unsupported.");

If this skip was added due to a known bug, it would be better to use QEXPECT_FAIL() here, so that when the bug is fixed the test clearly reports that it needs to be updated. (If this remains a QSKIP, there is no warning that the test is out-of-date and the bug could reappear without anybody being informed.) The QEXPECT_FAIL should refer to an appropriate bug report documenting the known bug.

If this test function is for a feature that is yet to be implemented, it should probably be removed unless the feature is on the roadmap.