Reviewed and applied spl-01-rm-gpl-symbol-set_cpus_allowed.patch

Reviewed and applied spl-01-rm-gpl-symbol-set_cpus_allowed.patch
from Ricardo which removes a dependency on the GPL-only symbol
set_cpus_allowed().  Using this symbol is simpler but in the name
of portability we are adopting a spinlock based solution here
to remove this dependency.

git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@160 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c