ParU: Explicitly include <cinttypes> in header that uses PRId64

[mmuetzel]

Potentially fixes #769.

[mmuetzel]

The build error for one of the demos of the SPEX library seems to be unrelated to this change.

[DrTimothyAldenDavis]

I see the problem in SPEX. An openmp for loop had for (int id = ...) where the value id is declared in the for loop itself. I just fixed it.

SPEX (to become v3.1) needs a threadprivate variable (via OpenMP or at __threads keyword) for thread safety (see

SuiteSparse/SPEX/SPEX_Utilities/Source/SPEX_gmp.c

Line 77 in e32105e

// SPEX is thread-safe as long as all of the following conditions hold:

), and spex_demo_threaded is a new demo program that tests this.