- Make local-only function and variables static.
- Move function prototypes and extern variable declarations to
header files.
- Delete unused variables.
There's still a handful of extern declaraions that should be fixed up.
an vector (struct) of function pointers. Add prototype declarations for
each vector entry.
Add declarations for the r2000 (MIPS-I) and r4000 (MIPS-III) locore
versions of the relevant functions.