RFA: m32r sim: Add prototypes for functions that pass/return DI values

[Nick Clifton]

Hi Simon,

> This kind of problem bit us in the past in GDB too.  I'd suggest trying
> to make the sim build system enable any or all of these warnings to
> catch such problems.
> 
>    -Wmissing-declarations
>    -Wmissing-prototypes
>    -Wold-style-declaration
>    -Wold-style-definition
>    -Wstrict-prototypes

I think that this would be an excellent idea.  Although I think
that it might cause a lot of work for the maintainers of cgen
based simulators.

Cheers
   Nick