Make V8_INT64_C() and V8_UINT64_C() available in 32-bit mode as well,
so we can write readable constants (base 10) instead of having to
obfuscate them using V8_2PART_UINT64_C().

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/23557002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16366 ce2b1a6d-e550-0410-aec6-3dcde31c8c00