ram_save_block is getting a bit too complicated, and does two separate
things:
   1) Finds a page to send
   2) Sends the page (dealing with compression etc)

Split into 'ram_save_page' to send the page and deal with compression (2)
Rename remaining function to 'ram_find_and_save_block'
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>