Add virDomainBlockPull support to the remote driver

Add virDomainBlockPull support to the remote driver

The generator can handle DomainBlockPullAll and DomainBlockPullAbort.
DomainBlockPull and DomainBlockPullInfo must be written by hand.

* src/remote/remote_protocol.x: provide defines for the new entry points
* src/remote/remote_driver.c daemon/remote.c: implement the client and
  server side
* src/remote_protocol-structs: structure definitions for protocol verification

Signed-off-by: Adam Litke <agl@us.ibm.com>