MBC-55x support virtually complete.

- I won't do any more, as I can't make the converter fully functional on a modern computer
- Basic typing support is working
- Some of the function modes move around the ASCII values, and this takes a while to decipher and figure out the pattern; it's not hard to do, and I don't really feel like doing it
- The hard part is already done :P

Keymap/keymap.h

@@ -49,6 +49,7 @@
 #include "hp150.h"
 #include "ibmconvertible.h"
 #include "kaypro1.h"
+#include "mbc55x.h"
 #include "microswitch8304.h"
 #include "skm67001.h"
 #include "sonynews.h"