scons: re-work the *Source functions to take more information.

Start by turning all of the *Source functions into classes
so we can do more calculations and more easily collect the data we need.
Add parameters to the new classes for indicating what sorts of flags the
objects should be compiled with so we can allow certain files to be compiled
without Werror for example.

src/sim/SConscript

@@ -41,7 +41,7 @@ Source('debug.cc')
 Source('eventq.cc')
 Source('faults.cc')
 Source('init.cc')
-BinSource('main.cc')
+Source('main.cc', bin_only=True)
 Source('pseudo_inst.cc')
 Source('root.cc')
 Source('serialize.cc')