hmp-commands: use long for begin and length in dump-guest-memory

hmp-commands: use long for begin and length in dump-guest-memory

The dump-guest-memory command is used to dump an area of guest memory
to a file, the piece of memory is specified by a begin address and
a length. These parameters are specified as ints and thus have a maximum
value of 4GB. This means you can't dump the guest memory past the first
4GB and instead get:
(qemu) dump-guest-memory tmp 0x100000000 0x100000000
'dump-guest-memory' has failed: integer is for 32-bit values
Try "help dump-guest-memory" for more information

This limitation is imposed in monitor_parse_arguments() since they are
both ints. hmp_dump_guest_memory() uses 64 bit quantities to store both
the begin and length values. Thus specify begin and length as long so
that the entire guest memory space can be dumped.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Message-Id: <20180620003202.10546-1-sjitindarsingh@gmail.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>