GXemul Code2

Attempting to fix a bug related to the integer types passed to UnitTest::Assert. (Problem noticed by Hollis Blanchard.)

Make the code compile on FreeBSD/Alpha 4.9 again (sys/types.h _must_ be included before sys/mman.h).

Beginning on a mainbus (MainbusComponent), which will forward reads and writes to other devices (such as RAM).

Minor update for nicer Doxygen output.

Making the counter in the ReferenceCountable class mutable, because const objects also need to be reference countable.

Adding a useful "todo" make target, which greps for all TODO strings in the source code.

Mention the mailing lists and IRC channel in the documentation.

Making the code compile cleanly with GNU C++' -pedantic. The
only module where -pedantic is not used is src/ir/, which needs
to cast e.g. uint8_t* to function pointer (for runtime
generated code).

Updating the TODO.

Adding dummy Save/SaveAs menu entries to the GTKMM UI. Also experimenting with graying out the Undo and Redo actions in the GUI (by querying the ActionStack).