[Truffle] Exclude some backtrace entries we don't want.
[Truffle] Don't try to convert exceptions that go all the way to the top level into Ruby backtraces.
[Truffle] Tidy up how internal exceptions are reported.
[Truffle] Quick hack to get STDOUT.flush.
[Truffle] Disable by default passing loop counts through blocks - pretty sure it's counterproductive.
[Truffle] Fix EOF in gets.