If it's not a regular file, don't return any data, even if the size is unknown.
Update the Zip test with a hand-tweaked Zip archive that has a
directory (with length-at-end set), a regular file without
length-at-end set, and a regular file with length-at-end set and a bad
CRC. Update the test code to verify that the file size is unset
for the regular file with length-at-end.
MFC after: 7 days
