DependencyTracker's @stack causes "SystemStackError: forwardable.rb:204: stack level too deep"

[sankl]

DependencyTracker::start's @stack gets improper state if compilation fails in Compiler::compile_rep method: ':visit_ended' event is not posted and last item never pops out. This leads to incorrect dependency graph and then to stack overflow during recursively checking outdated items in OutdatednessChecker::outdated_due_to_dependencies? is_outdated = ...

There are two solutions to this:

1. Compiler::compile_rep should 'ensure' that ':visit_ended' is posted.
   or
2. DependencyTracker::start should handle ':compilation_failed' and reset the @stack = []

[denisdefreyne]

This was fixed in #329 and released in 3.6.5.