SERVER-6572 fix Windows warning

Explicitly make the target of the bit shift 'long long' to avoid
MSVC warning: "src\mongo\db\record.cpp(242) : warning C4334:
'<<' : result of 32-bit shift implicitly converted to 64 bits
(was 64-bit shift intended?)".

src/mongo/db/record.cpp

@@ -239,7 +239,7 @@ namespace mongo {
             }
 
             inline size_t pageBitOf(size_t ptr) {
-                return 1 << ((ptr & pageSelectorMask) >> pageSelectorShift);
+                return 1LL << ((ptr & pageSelectorMask) >> pageSelectorShift);
             }
 
             inline size_t superpageOf(size_t ptr) {