GXemul Code2

Adding some TODOs about automated documentation generation.

Minor updates to the Doxygen class comment for MemoryMappedComponent, and to the Source code documentation Main Page.

Minor documentation fix.

Adding a MemoryMappedComponent base class, which all memory-
mapped components should inherit. (The canonical example is
the RAMComponent class.)

The MainBusComponent can now forward reads and writes to
memory-mapped child components.

Make parsing of hexadecimal values actually work. (It was never tested before, and was broken.)

Adding ROM (actually RAM :-) to the testmips machine, at 0xffffffffbfc00000.

Continuing on mainbus related things; moving the mips_cpu in the testmips machine so that it is placed on the mainbus.

Adding a dummy Emulation->Reset menu entry.

Unbreak parallel builds (make -j N).

Adding a TODO: Keep track of whether the document/emulation is "dirty"?