Fixes #4014: Move r30012 to v1.7 branch (ensure that comm_spawn'd procs get user-specified forwarded envars)

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r30012 [[BR]]
Ensure that comm_spawn'd procs get user-specified forwarded envars

Thanks to Tim Miller for reporting the regression from the 1.6 series

cmr=v1.7.4:reviewer=jsquyres:subject=Ensure that comm_spawn'd procs get user-specified forwarded envars
Fixes #4006: Move r29994 to v1.7 branch (Remove opal_recursion_depth_counter and opal_progress_thread_count. These)

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r29994 [[BR]]
Remove opal_recursion_depth_counter and opal_progress_thread_count. These counters add two
atomics in the critical path and are not currently used. We can bring them back if there
turns out to be a good use for them.

cmr=v1.7.4:reviewer=brbarret

r30027 [[BR]]
Remove remaining stale references

Refs #4006