restore: add helper for getting a temporary address of vma

A private vma will be mapped in a temporary place and an address will
be saved in vma->shmid, because nobody was used this field for private
vma-s before. For easy reading vma_premmapped_addr will be used for
getting the temporary address.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/image.h

@@ -94,6 +94,7 @@
 #define VMA_AREA_SYSVIPC	(1 <<  10)
 #define VMA_AREA_SOCKET		(1 <<  11)
 
+#define vma_premmaped_start(vma) ((vma)->shmid)
 #define vma_entry_is(vma, s)	(((vma)->status & (s)) == (s))
 #define vma_entry_len(vma)	((vma)->end - (vma)->start)