Get simple cpu to compile.

Get simple cpu to compile.

Now I need to fix linking errors, probably due to missing function details in new memory objects.

cpu/exec_context.cc:
cpu/exec_context.hh:
    Fix constructor for SE mode
cpu/simple/cpu.cc:
cpu/simple/cpu.hh:
    Fix compilation errors

--HG--
extra : convert_revision : 6a58c0906340e10b654369c36f528fc17e3f19be