Refactor QEMUFile for live migration

To support live migration, we override QEMUFile so that instead of writing to
disk, the save/restore state happens over a network connection.

This patch makes QEMUFile read/write operations function pointers so that we
can override them for live migration.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5352 c046a42c-6fe2-441c-8c8c-71466251a162
