Create a massively parallel test environment that reduces full testing of atlsh to less than 1 minute.

atltest

atltest is a wrapper around atltest and primarily serves to provide the correct environment from
the build and source source, as well as an automake-specific adjustment that affects the sequence of test-option and test-case.
Parallel testing under make check in automake requires the return code of a failed test. However, atltest doesn't provide it, so atltest.2.3.8 has been patched.
A large number of files in the tests directory were parallelized, which was necessary because TCL itself only supports sequential-testing.