[llvm] r199711 - tools: use 64-bit print specifier

[Tim Northover]

> Visual C++ 2013 has inttypes.h with PRIu64 but earlier versions do not.
> However, support/DataTypes.* defines these if needed.

Bother, thanks. I thought I'd grepped for them in our source
(remembering something along those lines). Clearly not well enough.

Tim.