Split prolongpointstru into search-only (prolongpointstru_search) and
append-only (prolongpointstru_append) functions. Parallelize shell-point
interpolation table construction with #pragma omp parallel for collapse(3)
and per-thread linked lists. Use static schedule for uniform workloads.
Add OMP_FLAG = -fopenmp in makefile.inc and ShellPatch.o override rule
in makefile for GCC OpenMP runtime (-lgomp already linked).
Speedup: setupintintstuff ~2.2x faster on multi-core.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
