Move iterator support functions out of ChapelArray and into a new module

Added a new internal module for iterator support functions and moved the
functions out of ChapelArray.  Updated tests that expected errors/warnings
from these functions to come from ChapelArray.  Updated a test that counts
dead modules to expect one more.
There wasn't a deep reason for moving it up.  I tried moving it down to just ahead of ChapelArray and release/examples was still fine.