If the dump file size does not fit in 32 bits, encode four zero bytes
(forcing an error for unmodified kpropd) followed by the size in the
next 64 bits.
Add a functional test case, but only run it when an environment
variable is set, as processing a 4GB dump file is too
resource-intensive for make check.
Resolves: rhbz#2133014
Signed-off-by: Julien Rische <jrische@redhat.com>
