This patch adds basic thermal support to gem5. It models energy dissipation
through a circuital equivalent, which allows us to use RC networks.
This lays down the basic infrastructure to do so, but it does not "work" due
to the lack of power models. For now some hardcoded number is used as a PoC.
The solver is embedded in the patch.
This patch adds the SubSystem container for grouping
simobjects together in logical subsystems to facilitate
building a larger system from constituent parts. The container
is simply a non-abstract empty simobject to hold the components
that will be connected as its children. In simulation the
object does not participate, its only use is during configuration
of the system.