Cleanup whitespace.
Make FPU independent from DRISC.

This patch removes the dependency on DRISC in the FPU model. Now FPU
declares its own IFPUClient interface, which can be implemented by any
component. DRISC::RegisterFile implements it.

As a side effect of this change a number of header dependencies have
been removed, resulting in slightly shorter build times and
finer-grained make dependencies.
New I/O message type: active messages (can be used for boot protocol).
Minor cleanup of the INVALID_* definitions.
Simplify the SMC.
Simplify the ActiveROM.
Let the ActiveROM send an active message upon boot (replaces SMC).
Cleanup whitespace.
Let DRISC::IOInterface discover its SMC automatically.
Perform register initialization in DRISC::Initialize.
Enable booting DRISC via active message on I/O.
Ensure registers are initialized after 1st thread is allocated.
Add missing include to fix compilation of area.cpp.
Simplify bundle creation.
Avoid failing if :InitReg is not present in configuration.
Allow for heterogeneous CDMA:Cache configurations (selector/sets/assoc).
Fix the CACTI area computation for CDMA.
Allow connecting DRISC to memory after construction.
Cleanup whitespace.
Document the core interface in the simulator.