Fix 9 warnings about type specifiers under Linux

Under some 64-bit Linux, 64-bit types are unsigned long.
Under 64-bit OS X and some other Linux, 64-bit types are unsigned long long.

This makes manually specifying format types impossible unless you
cast or use system-provided specifiers.

Let's use the system provided C99 format type specifier abstraction so
the system provides `%lu` or `%llu` depending on what works on that system.

Before this patch, `unstable` fails `gcc` and `clang` `-Werror` compiles: https://travis-ci.org/mattsta/redis/builds/21894346

Using this patch, the warnings go away and all tests pass now: https://travis-ci.org/mattsta/redis/builds/21896098