* Provide a new API compile_file_prism which mirrors compile_file
but uses prism to parse/compile.
* Provide the ability to run test-all with RUBY_ISEQ_DUMP_DEBUG set
to "prism". If it is, we'll use the new compile_file_prism API to
load iseqs during the test run.
parallel test (`make test-all TESTS=-j8`) runs tests on specified
number of processes. However, some test checkers written in
`runner.rb` are not loaded. This fix enable these checkers on
parallel tests.
See also: https://github.com/ruby/ruby/pull/2508
