The existing xc_domain_dumpcore is very specific to disk/file based
output.  Refactor the code slightly to allow more user-specified
control.  This is done by adding a parallel xc_domain_dumpcore2 (naming
isn't always my strong suit), which allows the specification of a
callback routine and an opaque argument block.  The existing dumpcore
routine is modified to use the callback for all write operations and
to turn the single seek into a small write (it's for page alignment).

I've also included a small test routine, testdump.c, which drives
both APIs and allows writing core to either a local disk file or
across a network.  And, I've included a sample network "catcher"
program that receives a cross-network dump from testdump.

And, good news, this probably ends my current hacking/interest
in xc_domain_dumpcore.


Signed-off-by: Ben Thomas (bthomas@virtualiron.com)

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Ben Thomas                                         Virtual Iron Software
bthomas@virtualiron.com                            Tower 1, Floor 2
978-849-1214                                       900 Chelmsford Street
                                                    Lowell, MA 01851