syscall_emul: [patch 8/22] refactor process class

Moves aux_vector into its own .hh and .cc files just to get it out of the
already crowded Process files. Arguably, it could stay there, but it's
probably better just to move it and give it files.

The changeset looks ugly around the Process header file, but the goal here is
to move methods and members around so that they're not defined randomly
throughout the entire header file. I expect this is likely one of the reasons
why I several unused variables related to this class. So, the methods are
declared first followed by members. I've tried to aggregate them together
so that similar entries reside near one another.

There are other changes coming to this code so this is by no means the
final product.

src/sim/SConscript

@@ -75,6 +75,7 @@ Source('mathexpr.cc')
 if env['TARGET_ISA'] != 'null':
     SimObject('InstTracer.py')
     SimObject('Process.py')
+    Source('aux_vector.cc')
     Source('faults.cc')
     Source('process.cc')
     Source('fd_entry.cc')