Migration: Support systems with more than 32 CPUs.

This patch improves the cpu bit map parsing used to determine
CPU/cluster mapping. Namely, it supports clusters with more
than 32 CPUs. Prior to this patch, mapping would fail due to
unexpected commas in bitfield data read from /proc (groups
of 32 CPUs are separated by commas).

NOTE: Bug could still be encountered if NR_CPUS > 32.

New CPU limit: 4096.
FIX: Add S_IRUSR to open() for DFLP.

This patch adds S_IRUSR as the third parameter to open()
in the DFLP locking unit test.