- Move common defs and helper functions to check_util.h/check_utils.c.
- Add a prepare script argument for ATX_CHECK_FS* macros.
- ASSERT_EXPR_INT(): Use long int as expression result type.
- Other misc updates.
- Do not exit with status 99. It is considered a "hard failure"
in Autotest, and cleanup script won't be executed.
- Fix ATX_FEAT_PREREQ().
- Remove unneeded helper macros.
- Add more log output.
