[RFA] Top level configury additions for RDA (2nd try)

[DJ Delorie]

> Any objections to the following additions to the top level configury?
> 
> (Thanks to DJ and Nathanael for telling me about Makefile.def and autogen.)
> 
> 	* Makefile.def (host_modules): Add rda.
> 	* Makefile.in: Regenerate.
> 	* configure.in (configdirs): Add rda to list of directories
> 	to configure for certain hosts.

This is fine.  Please apply to both gcc and src.