Mac OS/X 32 bit build broken at commit 1a2cc27e013b561c9d3c8b81384d14443822057f

[warrenfalk]

Mac 32 bit build now fails with the following error:

db/column_family.cc:152:38: error: non-type template argument evaluates to 68719476736, which cannot be narrowed to type 'unsigned long' [-Wc++11-narrowing]
      std::integral_constant<size_t, 64ull << 30>>::type::value;
                                     ^
1 error generated.