PR libgomp/42942
* env.c (parse_unsigned_long): Add ALLOW_ZERO argument.
(initialize_env): Adjust callers.
(omp_set_max_active_levels): Set gomp_max_active_levels_var even
when the argument is 0.
* testsuite/libgomp.c/pr42942.c: New test.
From-SVN: r157635