Perl extension managing OpenMP variables in %ENV within a script.

Changes for 1.2.0

• fixing inconsistencies along side of the development of OpenMP::Simple, which is exposing some hidden issues.
• using omp_dynamic to set OMP_DYNAMIC with a falsy value results in the key getting deleted; this may end up being how all "boolean" envars are handled
• added a couple more envars missing neede to support the upcoming OpenMP::Simple trial release