Use Standard Integers Directly

[insertinterestingnamehere]

We currently have an old header generation script to correctly pull in the integer types that are normally defined in stdint.h. It existed primarily for compatibility with implementations that didn't provide those headers in the right places. This hasn't been a concern with current compilers for many years and we should drop that functionality and use stdint.h directly instead of qthreads-int.h.

The relevant generation script is: https://github.com/sandialabs/qthreads/blob/619afe98edce0098f656c32acf09a12789becad0/config/ax_create_stdint_h.m4