Export release_pages; nice undo for get_user_pages.

Andrew Morton suggests tun/tap use release_pages, but it's not
exported.  It's not clear to me why this is in swap.c, but it exists
even without CONFIG_SWAP, so that's OK.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-By: Andrew Morton (not the biographer, the other one)
---
 mm/swap.c |    1 +
 1 file changed, 1 insertion(+)

diff -r abd2ad431e5c mm/swap.c
--- a/mm/swap.c	Sat Apr 19 00:34:54 2008 +1000
+++ b/mm/swap.c	Sat Apr 19 01:11:40 2008 +1000
@@ -346,6 +346,7 @@ void release_pages(struct page **pages, 
 
 	pagevec_free(&pages_to_free);
 }
+EXPORT_SYMBOL(release_pages);
 
 /*
  * The pages which we're about to release may be in the deferred lru-addition
