[perl #128275] [BUG] Circular module dependency is not detected; causes program to hang

[Sam S. via RT]

Relevant info from IRC discussion:

  psch:   we did have circular module loading detection at some point... 
probably got clobbered with all the CUR work though :/
  lizmat: before, the detection lived in the nqp code, if I recall
  lizmat: now, it is the responsibility of the CUR to detect circularities
  lizmat: a start would be writing a test  :-)