Many tests didn't change back from subdirectories at the end of the tests ...
and they don't have to. The missing 'cd ..' could always be added when another
test case is added to the test file.
This change do that tests (99.5%) consistently end up in $TESTDIR where they
started, thus making it simpler to extend them or move them around.
Globbing is usually used for filenames, so on windows it is reasonable and very
convenient that glob patterns accepts '\' or '/' when the pattern specifies
'/'.
This is extremely handy for those occasional circumstances where you
need to edit .hg/sharedpath manually, since modern Unix text editors
make it surprisingly difficult to create a text file with no trailing
newline.
