QFile autotest has disabled invalidFile test function

In tests/auto/corelib/io/qfile/tst_qfile.cpp, the invalidFile test function is disabled (by virtue of the fact that it is no longer a slot) with a comment that the test hangs. The test function was disabled before the tests were imported into the Qt repository in June 2006, so thee is no further evidence. I'm presuming that the test hung on Windows, as it currently passes on Unix if turned back into a slot.

Please investigate whether the test still hangs. If not, the test should be re-enabled. If the test does hang, it should be determined whether the test or the Qt libraries are at fault.