Add a LowLevel watch interface and use it to build an @introduceDomain watcher

We now have 2 sources of 'something has changed' events:

- the VIRQ_DOM_EXC used by Xenstored
- @introduceDomain and @releaseDomain watching, as used by everyone else

This patch also includes an example which shows how to watch for domain events.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Regenerate OASIS

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
getdomaininfolist: return Val_int, not Int_val

This caused the "int" which was supposed to be 0 to not be
equal to the literal 0.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
userspace: Io_page.get takes pages, not bytes

Listing domains in batches of 512 should be adequate (not batches of
2M)

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Userspace: remove commented-out code

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Start removing the broken buffering support

I think it's better to enhance the shared-memory-ring to produce
larger in-memory rings rather than an ad-hoc solution here.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
We need xenctrl.h to compile the domaininfolist-based domain watcher

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #10 from djs55/add-userspace-watch

Add a domain watcher example