Don't go past the end of a page in a NetScaler file.

Don't go past the end of a page in a NetScaler file.

Records in a properly formatted NetScaler file shouldn't go past the end
of a page, but nothing guarantees that a NetScaler file will be properly
formatted.

NetScaler 3.x files allow record bodies to go past the end of a page,
but 1.x and 2.x files don't, so treat record headers that go past the
end of a page, and record bodies in 1.x and 2.x files that go past the
end of a page, as errors.

Clean up some stuff while we're at it.

Bug: 13430
Change-Id: I3b1d56086e3bb14b246406f306e3d730df337561
Reviewed-on: https://code.wireshark.org/review/20326
Reviewed-by: Guy Harris <guy@alum.mit.edu>