Fixes #4000: Move r29983 to v1.7 branch (fix sparc sigbus in opal net code)

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r29983 [[BR]]
Fixes #3990: ensure we don't SIGBUS on SPARC by forcing a memory copy
and preventing access to potentially unaligned data.

Reviewed by Dave Goodell.  Tested by Siegmarr Gross.

cmr=v1.7.4:reviewer=ompi-rm1.7:subject=fix SPARC SIGBUS in opal net code