Fix undefined type in StopWatch::toHuman

[mwootten]

Use unsigned long long instead of uint64_t in StopWatch::toHuman. Since isn't explicitly imported, using uint64_t breaks compilation with gcc 13.1.1; it was probably included by another header in the past. Additionally, this makes it consistent with the rest of the function.

[kamahen]

uint64_t is defined by doing:
#include #include <cstdint> in StopWatch.hpp and changing unsigned long long to uint64_t in both StopWatch.hpp and StopWatch.cpp.

There are quite a few other places where unsigned long long is used ... the exact definition of this is platform-dependent, so uint64_t is probably better.

Other files use uint64_t without <cstdint>, so probably something one of the other <c...> includes works instead.

[kamahen]

This compiles with gcc-12.2.0 (but with lots of warnings; gcc-13.2.0 also has lots of warnings).