Merge remote-tracking branch 'quintela/migration-next-20121017' into staging

Merge remote-tracking branch 'quintela/migration-next-20121017' into staging

* quintela/migration-next-20121017: (41 commits)
  cpus: create qemu_in_vcpu_thread()
  savevm: make qemu_file_put_notify() return errors
  savevm: un-export qemu_file_set_error()
  block-migration: handle errors with the return codes correctly
  block-migration:  Switch meaning of return value
  block-migration: make flush_blks() return errors
  buffered_file: buffered_put_buffer() don't need to set last_error
  savevm: Only qemu_fflush() can generate errors
  savevm: make qemu_fill_buffer() be consistent
  savevm: unexport qemu_ftell()
  savevm: unfold qemu_fclose_internal()
  savevm: make qemu_fflush() return an error code
  savevm: Remove qemu_fseek()
  virtio-net: use qemu_get_buffer() in a temp buffer
  savevm: unexport qemu_fflush
  migration: make migrate_fd_wait_for_unfreeze() return errors
  buffered_file: make buffered_flush return the error code
  buffered_file: callers of buffered_flush() already check for errors
  buffered_file: We can access directly to bandwidth_limit
  buffered_file: unfold migrate_fd_close
  ...