systemc: Partially implement the sc_module_name class.

This class is mostly implemented as defined by the spec, except that
it doesn't maintain the module name stack (which doesn't yet exist).

Change-Id: I05fdc4aa40fb0497b0165824baee87ebf01a7821
Reviewed-on: https://gem5-review.googlesource.com/10823
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/systemc/SConscript

@@ -32,4 +32,5 @@ if env['USE_SYSTEMC']:
 
     Source('kernel.cc')
 
+    Source('sc_module_name.cc')
     Source('sc_object.cc')