This option limits the number of threads per core created in SMT machines, while
keeping the same affinity mask by binding to multiple hwthreads inside the core.

Setting the typedef name to a more representative name. Also, it allows use the PEList name to implement a real list of PEs

This reverts commit ff81a05b, reversing
changes made to 60a04672.

The invalidation_improvements branch needs more testing on its own,
after merging some applications stopped to work correctly, so
there is something wrong in that branch.
The subsequent commits are also reverted, except the one bumping
the version to 0.12a.

Split the SMPPlugin code into .cpp/_decl.hpp and set the private variables to protected so other Plugins can inherit from it (TaskSim).