Silence compiler warning on 64-bit windows build

src/backend/utils/mmgr/aset.c

@@ -11,7 +11,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/mmgr/aset.c,v 1.80 2009/07/21 19:53:12 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/mmgr/aset.c,v 1.81 2010/01/01 19:57:07 mha Exp $
  *
  * NOTE:
  *	This is a new (Feb. 05, 1999) implementation of the allocation set
@@ -698,11 +698,11 @@ AllocSetAlloc(MemoryContext context, Size size)
 				 * freelist than the one we need to put this chunk on.	The
 				 * exception is when availchunk is exactly a power of 2.
 				 */
-				if (availchunk != (1 << (a_fidx + ALLOC_MINBITS)))
+				if (availchunk != ((Size) 1 << (a_fidx + ALLOC_MINBITS)))
 				{
 					a_fidx--;
 					Assert(a_fidx >= 0);
-					availchunk = (1 << (a_fidx + ALLOC_MINBITS));
+					availchunk = ((Size) 1 << (a_fidx + ALLOC_MINBITS));
 				}
 
 				chunk = (AllocChunk) (block->freeptr);